KR102285852B1 - Method and apparatus for communication in full dimension mimo mobile communication system - Google Patents

Abstract

A method for transmitting and receiving channel state information in a terminal including a plurality of antennas according to an embodiment of the present specification includes: receiving a reference signal corresponding to a first dimension from a base station; determining precoding information corresponding to the first dimension based on the reference signal corresponding to the first dimension; determining precoding information corresponding to a second dimension based on preset precoding combination information; and transmitting the channel state information determined based on the precoding information corresponding to the first dimension and the precoding information corresponding to the second dimension to the base station. According to the embodiment of the present specification, the base station and the terminal including a plurality of antennas accurately transmit and receive precoding information and channel state information, and it is possible to reduce overhead occurring during transmission and reception.

Description

Communication method and device in all-dimensional multiple input multiple output mobile communication system {METHOD AND APPARATUS FOR COMMUNICATION IN FULL DIMENSION MIMO MOBILE COMMUNICATION SYSTEM}

An embodiment of the present specification relates to a wireless mobile communication system, and in particular, in a wireless mobile communication system to which a multiple access scheme using a multi-carrier, such as OFDMA: Orthogonal Frequency Division Multiple Access, is applied. A method for transmitting and receiving PMI and channel state information for measuring channel quality (radio channel state) and notifying the base station to operate as a Hybrid MIMO system.

The current mobile communication system is developing into a high-speed, high-quality wireless packet data communication system to provide data service and multimedia service, away from the initial voice-oriented service provision. To this end, various standardization organizations such as 3GPP, 3GPP2, and IEEE are proceeding with the 3rd generation evolutionary mobile communication system standard applying multiple access method using multi-carrier. Recently, various mobile communication standards, such as 3GPP's Long Term Evolution (LTE), 3GPP2's Ultra Mobile Broadband (UMB), and IEEE's 802.16m, provide high-speed, high-quality wireless packet data transmission services based on multiple access methods using multi-carriers. was developed to support

Existing 3G evolutionary mobile communication systems such as LTE, UMB, and 802.16m are based on the multi-carrier multiple access method, and to improve transmission efficiency, Multiple Input Multiple Output (MIMO, multiple antennas) is applied and beam- It has the characteristics of using various techniques such as forming (beamforming), Adaptive Modulation and Coding (AMC, adaptive modulation and coding) method, and channel sensitive scheduling method. The above various technologies improve transmission efficiency through methods such as concentrating transmission power transmitted from multiple antennas or controlling the amount of transmitted data according to channel quality, etc., and selectively transmitting data to users with good channel quality. Improve system capacity performance. Since most of these techniques operate based on channel state information between a base station (eNB: evolved Node B, BS: base station) and a user equipment (UE: User Equipment, MS: Mobile Station), an eNB or UE is a base station and a terminal. It is necessary to measure the channel state between the two, and in this case, a Channel Status Indication reference signal (CSI-RS) may be used. The aforementioned eNB means a downlink transmission and an uplink reception device located at a certain place, and one eNB may perform transmission/reception for a plurality of cells. A plurality of eNBs may be geographically dispersed in one mobile communication system, and each eNB performs transmission/reception for a plurality of cells.

Existing 3G and 4G mobile communication systems such as LTE/LTE-A utilize MIMO technology that transmits using a plurality of transmit/receive antennas to expand data rates and system capacity. The MIMO technology may spatially separate and transmit a plurality of information streams by using a plurality of transmit/receive antennas. In this way, spatially separating and transmitting a plurality of information streams is called spatial multiplexing. In general, the number of information streams to which spatial multiplexing can be applied depends on the number of antennas of the transmitter and receiver. In general, the number of information streams to which spatial multiplexing can be applied is called the rank of the transmission. In the case of MIMO technology supported by standards up to LTE/LTE-A Release 11, spatial multiplexing is supported when there are 8 transmit/receive antennas, respectively, and up to 8 ranks are supported. On the other hand, the FD-MIMO system may include a case where the existing LTE/LTE-A MIMO technology has evolved and 32 or more transmit antennas, which are more than 8, are used. A method and apparatus for transmitting a channel state in such an FD-MIMO system are required.

The purpose of the embodiment of the present specification is to measure a reference signal in a terminal for a hybrid MIMO of a new concept that possesses both the advantages of open-loop MIMO and closed-loop MIMO in FD-MIMO transmission and reception, generation of channel state information, and transmission of channel state information It may include providing a method and apparatus for It may also include providing a method and apparatus for transmitting a reference signal from a base station to a terminal and receiving channel state information transmitted by the terminal. .

A method for transmitting and receiving channel state information in a terminal including a plurality of antennas according to an embodiment of the present specification includes: receiving a reference signal corresponding to a first dimension from a base station; determining precoding information corresponding to the first dimension based on the reference signal corresponding to the first dimension; determining precoding information corresponding to a second dimension based on preset precoding combination information; and transmitting the channel state information determined based on the precoding information corresponding to the first dimension and the precoding information corresponding to the second dimension to the base station.

According to another embodiment of the present specification, a method for transmitting and receiving channel state information in a base station including a plurality of antennas includes transmitting a reference signal corresponding to a first dimension to a terminal; and receiving, from the terminal, channel state information determined based on the reference signal corresponding to the first dimension, wherein the terminal includes a free signal corresponding to the first dimension based on the reference signal corresponding to the first dimension. Determining coding information, determining precoding information corresponding to a second dimension based on preset precoding combination information, and matching the channel state information to precoding information corresponding to the first dimension and the second dimension It is characterized in that it is determined based on the precoding information.

A terminal of a mobile communication system according to another embodiment of the present specification includes a transmitting/receiving unit including a plurality of antennas and transmitting and receiving signals to and from a base station; and controlling the transceiver, receiving a reference signal corresponding to the first dimension from the base station, determining precoding information corresponding to the first dimension based on the reference signal corresponding to the first dimension, and performing preset precoding Precoding information corresponding to the second dimension is determined based on the combination information, and channel state information determined based on the precoding information corresponding to the first dimension and the precoding information corresponding to the second dimension is transmitted to the base station. It includes a control unit for transmitting.

A base station of a mobile communication system according to another embodiment of the present specification includes a transceiver unit including a plurality of antennas and transmitting and receiving signals to and from the terminal;

a control unit for controlling the transceiver, transmitting a reference signal corresponding to the first dimension to the terminal, and receiving channel state information determined based on the reference signal corresponding to the first dimension from the terminal, the terminal comprising: Determine the precoding information corresponding to the first dimension based on the reference signal corresponding to the first dimension, determine the precoding information corresponding to the second dimension based on preset precoding combination information, and the channel state It is characterized in that the information is determined based on the precoding information corresponding to the first dimension and the precoding information corresponding to the second dimension.

According to the embodiment of the present specification, the base station and the terminal including a plurality of antennas accurately transmit and receive precoding information and channel state information, and it is possible to reduce overhead occurring during transmission and reception.

1 illustrates an FD-MIMO system according to an embodiment of the specification.
FIG. 2 shows radio resources of 1 subframe and 1 Resource Block (RB) in an LTE/LTE-A system.
3A and 3B are diagrams illustrating a CSI-RS transmission method according to an embodiment.
4 illustrates that the UE transmits RI, PMI, and CQI for 2D-CSI-RS according to an embodiment.
5 is a diagram illustrating that the UE transmits RI, PMI, and CQI for a plurality of CSI-RSs according to an embodiment.
6 is a diagram illustrating _{that precoding corresponding to PMI H} is allocated as open-loop MIMO and defined according to time and frequency resources according to an embodiment.
7 is a diagram illustrating _{that precoding corresponding to PMI V} is allocated as open-loop MIMO and defined according to time and frequency resources according to an embodiment.
_{8 is a diagram illustrating that a UE transmits RI V} and PMI _V to a base station according to method 1 of defining a precoding set according to a resource according to an embodiment.
_{9 is a diagram illustrating that the terminal transmits RI V} and PMI _V to the base station using method 2 of defining a precoding set according to a resource according to an embodiment.
10 illustrates an example in which a base station and two terminals assume precoding definition method 1 for each subband according to an embodiment.
11 illustrates an example in which a base station and two terminals assume precoding definition method 2 for each subband according to an embodiment.
12 illustrates an example in which a base station and two terminals assume a predcoding definition method 3 for each subband according to an embodiment.
13 illustrates an example in which a base station and two terminals assume a precoding definition method 4 for each subband according to an embodiment.
14 illustrates an example of defining time and frequency resources in advance for defining a _{plurality of precoding sets {PMI H} , PMI _V } by a base station and a terminal using a precoding definition method 5 for each subband according to an embodiment. .
15 is a diagram illustrating a method of pre-defining _{PMI H} for each time and frequency resource according to the wideband-specific precoding definition method 1 in each terminal according to an embodiment.
16 is a diagram illustrating a method of pre-defining _{PMI V} for each time and frequency resource according to method 2 for defining precoding for each wideband in each terminal according to an embodiment.
17 is a diagram illustrating a method of pre-defining _{PMI H} and PMI _V for each terminal according to the wideband-specific precoding definition method 3 for each terminal according to an embodiment.
18 is a diagram illustrating a method of pre-defining _{PMI V} and PMI _H for each terminal according to the wideband-specific precoding definition method 4 for each terminal according to an embodiment.
19 illustrates an example of defining time and frequency resources for defining _{a plurality of precoding sets {PMI H} , PMI _V } in advance using the precoding definition method 5 for each wideband according to an embodiment.
20 is a diagram illustrating an operation of a base station in method 1 of defining one precoding according to a resource according to an embodiment of the present specification.
21 is a diagram illustrating the operation of a terminal in method 1 of defining one precoding according to a resource according to an embodiment of the present specification.
22 is a diagram illustrating an operation of a base station in method 2 of defining one precoding according to a resource according to an embodiment of the present specification.
23 is a diagram illustrating the operation of a terminal in method 2 of defining one precoding according to a resource according to an embodiment of the present specification.
24 is a diagram illustrating an operation of a base station in method 1 of defining a precoding set according to a resource according to an embodiment of the present specification.
25 is a diagram illustrating the operation of a terminal in method 1 of defining a precoding set according to a resource according to an embodiment of the present specification.
26 is a diagram illustrating the operation of a base station in method 2 of defining a precoding set according to a resource according to an embodiment of the present specification.
27 is a diagram illustrating the operation of a terminal in method 2 of defining a precoding set according to a resource according to an embodiment of the present specification.
28 is a diagram illustrating an apparatus of a base station in an FD-MIMO system according to an embodiment of the present specification.
29 is a diagram illustrating a device of a terminal in an FD-MIMO system according to an embodiment of the present specification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In describing the embodiments, descriptions of technical contents that are well known in the technical field to which the present invention pertains and are not directly related to the present invention will be omitted. This is to more clearly convey the gist of the present invention without obscuring the gist of the present invention by omitting unnecessary description.

For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings. In addition, the size of each component does not fully reflect the actual size. In each figure, the same or corresponding elements are assigned the same reference numerals.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may in fact be performed substantially simultaneously, or it is possible that the blocks are sometimes performed in the reverse order according to the corresponding function.

At this time, the term '~ unit' used in this embodiment means software or hardware components such as FPGA or ASIC, and '~ unit' performs certain roles. However, '-part' is not limited to software or hardware. The '~ unit' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Thus, as an example, '~' denotes components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to play one or more CPUs in a device or secure multimedia card.

Hereinafter, embodiments of the present specification will be described in detail with reference to the accompanying drawings. Also, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention in describing the embodiment, the detailed description thereof may be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

In addition, in describing the embodiments of the present specification in detail, the OFDM-based wireless communication system, particularly the 3GPP EUTRA standard, will be mainly targeted, but the main subject of the present specification is other communication systems having a similar technical background and channel type. It is also applicable as a modification within a range that does not significantly depart from the scope of the embodiments of the present specification, which will be possible by the judgment of a person having technical knowledge skilled in the technical field of the embodiments of the present specification.

A reference signal is a data symbol received by measuring the channel status between the base station and users, such as channel strength or distortion, interference strength, and Gaussian noise in a wireless mobile communication system. A signal used to aid in demodulation and decoding. Another use of the reference signal is the measurement of radio channel conditions. The receiver may determine the state of the radio channel between itself and the transmitter by measuring the reception strength at which the reference signal transmitted by the transmitter with the promised transmission power is received through the radio channel. The determined state of the radio channel may be used to determine what data rate the receiver will request from the transmitter.

In recent 3rd generation evolutionary wireless mobile communication system standards such as 3GPP LTE/LTE-A or IEEE 802.16m, multiple subcarriers such as OFDM(A) (orthogonal frequency division multiplexing (multiple access)) are used as multiple access techniques. A multiple access method is mainly adopted. In the case of a wireless mobile communication system to which the multiple access technique using the multiple subcarriers is applied, channel estimation and measurement are performed according to how many time symbols and subcarriers a reference signal is to be located in time and frequency. ), there is a difference in performance. In addition, channel estimation and measurement performance may be affected by how much power is allocated to the reference signal. Accordingly, if more radio resources such as time, frequency, and power are allocated to the reference signal, channel estimation and measurement performance is improved, demodulation and decoding performance of a received data symbol is improved, and the accuracy of channel state measurement is also increased.

However, in the case of a general mobile communication system, since radio resources such as time, frequency, and transmission power for transmitting a signal are limited, when many radio resources are allocated to a reference signal, radio resources that can be allocated to a data signal This is relatively reduced. For this reason, the radio resource allocated to the reference signal should be appropriately determined in consideration of system throughput. In particular, when MIMO (Multiple Input Multiple Output) that transmits and receives using a plurality of antennas is applied, it is a very important technical matter to allocate a reference signal and measure it.

Such a MIMO system may transmit a PMI (Precoder Matrix Indicator) designating precoding for optimizing system performance using channel information on the receiver side obtained through a reference signal when forming a transmission beam pattern. The MIMO system may be divided into a closed-loop MIMO system or an open-loop MIMO system according to whether the receiver side transmits such PMI information.

In the case of a closed-loop MIMO system, the terminal uses a reference signal to determine channel information and to determine the characteristics of the corresponding channel through this. Using these channel characteristics, the optimal precoding is selected from among the precoder sets supported by the current radio channel, and the optimal precoding is obtained and transmitted to the base station through PMI. In addition, assuming that the derived precoding is used, the maximum data rate is obtained assuming the current radio channel, and this is fed back to the base station through the CQI (Channel Quality Indicator). The base station receiving such feedback can communicate with the terminal using transmission/reception precoding appropriate to the terminal based on the corresponding information.

In the case of an open-loop MIMO system, unlike a closed-loop MIMO system, the receiver does not transmit PMI information to the transmitter, but instead, the transmitter and the receiver determine and use precoding according to time and frequency resources. can In this case, the receiver receives the reference signal through the corresponding precoding, and uses the result to transmit the quality of the radio channel to the transmitter through CQI as in the closed-loop MIMO system. The base station that has received the CQI determines how the terminal should communicate based on the corresponding information.

In general, it is known that closed-loop MIMO exhibits greater system performance than open-loop MIMO because channel information can be adaptively used. However, for this, additional overhead such as PMI is required, and performance loss due to dynamic interference in which a beam pattern of an interference signal rapidly changes with time may occur in a situation in which the mobile speed of the terminal is very fast or the channel changes rapidly.

On the other hand, in the case of an open-loop MIMO system, the performance efficiency of the system itself is lower than that of a closed-loop MIMO system, but there are advantages such as less influence of dynamic interference and less feedback overhead for PMI.

As mentioned above, since both closed-loop MIMO and open-loop MIMO have their respective advantages, the latest 3G evolutionary wireless mobile communication system standards such as 3GPP LTE(-A) or IEEE 802.16m support selective use of them. are doing However, in a system such as FD-MIMO (Full Dimension-MIMO) that has a plurality of transmit antennas and operates a plurality of reference signals, each reference signal can selectively operate a closed-loop MIMO or an open-loop MIMO system, respectively. In the technology and apparatus using the Hybrid MIMO system proposed in the embodiment of the present specification, when the channel state measurement method using a plurality of reference signals is made so that the terminal effectively measures the radio channel state information, some of the plurality of reference signals are In order to operate as an open-loop MIMO system, it is operated using a predefined PMI, and for the remaining reference signals, an optimal PMI can be found and transmitted to the base station through an uplink control channel to operate as a closed-loop MIMO system. In addition, CQI information indicating a terminal supportable data rate generated on the assumption that horizontal and vertical precoding is simultaneously applied by combining a predetermined PMI and an optimal PMI corresponding to an open-loop MIMO system. Also, an uplink control channel is provided to the base station. will be transmitted through

The FD-MIMO system refers to a wireless communication system that transmits data using tens or more of transmit antennas.

1 illustrates an FD-MIMO system according to an embodiment of the specification.

Referring to FIG. 1 , the base station 100 transmitting equipment may include tens or more transmitting antennas, and may transmit a radio signal through one or more of the transmitting antennas. A plurality of transmission antennas are arranged to maintain a minimum distance from each other as in the case of identification number 110. An example of the minimum distance is half the wavelength of the transmitted radio signal. In general, when a distance equal to half the wavelength of a radio signal is maintained between transmitting antennas, signals transmitted from each transmitting antenna are affected by a radio channel having a low correlation with each other. For example, when the band of the transmitted wireless signal is 2 GHz, this distance is 7.5 cm, and when the band is higher than 2 GHz, this distance may be shorter.

In FIG. 1 , dozens or more of the transmitting antennas disposed in the base station 100 are used to transmit signals such as at least one of identification numbers 120 and 130 to one or a plurality of terminals. In an embodiment, appropriate precoding may be applied to a plurality of transmission antennas to transmit simultaneously to a plurality of terminals. In this case, one terminal may receive one or more information streams. In general, the number of information streams that one terminal can receive is determined according to the number of reception antennas and channel conditions possessed by the terminal.

In order to effectively implement the FD-MIMO system, the UE must accurately measure the channel condition and the size of interference, and use it to effectively transmit the channel condition information to the base station. The base station receiving the channel state information can determine which terminals to transmit to, which data rate to transmit, and which precoding to apply in connection with downlink transmission by using it. In the case of the FD-MIMO system, since the number of transmission antennas is large, when the conventional method of transmitting and receiving channel state information of the LTE/LTE-A system is applied, an uplink overhead problem of transmitting a lot of control information in the uplink may occur. there is.

In a mobile communication system, time, frequency, and power resources are limited. Therefore, if more resources are allocated to the reference signal, the resources that can be allocated for transmission of a traffic channel decrease, and thus the absolute amount of transmitted data may decrease. In this way, when more resources are allocated to the reference signal, the performance of channel measurement and estimation is improved, but the absolute amount of data that can be transmitted is reduced, so the overall system capacity performance may be rather deteriorated. Therefore, it is necessary to properly allocate a resource for a reference signal and a resource for a signal for transmission of a traffic channel in order to derive optimal performance in terms of overall system capacity.

FIG. 2 shows radio resources of 1 subframe and 1 Resource Block (RB) in an LTE/LTE-A system.

Referring to FIG. 2 , the illustrated radio resource consists of one subframe on the time axis and one RB on the frequency axis. Such a radio resource consists of 12 subcarriers in the frequency domain and 14 OFDM symbols in the time domain to have a total of 168 unique frequencies and time positions. In LTE/LTE-A, each natural frequency and time position of FIG. 2 is referred to as a resource element (RE).

A plurality of different types of signals as follows may be transmitted to the radio resource shown in FIG. 2 .

1. CRS (Cell Specific RS): A reference signal periodically transmitted for all terminals belonging to one cell and can be commonly used by a plurality of terminals.

2. DMRS (Demodulation Reference Signal): A reference signal transmitted for a specific terminal and transmitted only when data is transmitted to the corresponding terminal. DMRS may consist of a total of 8 DMRS ports. In LTE/LTE-A, port 7 to port 14 correspond to DMRS ports, and ports maintain orthogonality so that they do not interfere with each other using CDM or FDM.

3. PDSCH (Physical Downlink Shared Channel): This is a data channel transmitted through downlink, which is used by the base station to transmit traffic to the UE and is transmitted using REs in which a reference signal is not transmitted in the data region of FIG. 2 .

4. CSI-RS (Channel Status Information Reference Signal): A reference signal transmitted for terminals belonging to one cell is used to measure the channel state. A plurality of CSI-RSs may be transmitted to one cell.

5. Other control channels (PHICH, PCFICH, PDCCH): ACK/NACK transmission for providing control information necessary for the UE to receive the PDSCH or operating HARQ for uplink data transmission

In addition to the above signals, in the LTE-A system, muting may be set so that CSI-RSs transmitted by other base stations can be received without interference by terminals of the corresponding cell. The muting may be applied at a position where CSI-RS can be transmitted, and in general, the UE receives a traffic signal by skipping the corresponding radio resource. In the LTE-A system, muting is another term called zero-power CSI-RS. This is because, due to the nature of muting, it is applied to the location of the CSI-RS and transmission power is not transmitted.

In FIG. 2, the CSI-RS is to be transmitted using a part of the positions indicated by A, B, C, D, E, E, F, G, H, I, J according to the number of antennas for transmitting the CSI-RS. can Also, muting can be applied to some of the positions indicated by A, B, C, D, E, E, F, G, H, I, J. In particular, the CSI-RS may be transmitted with 2, 4, or 8 REs according to the number of transmitting antenna ports. When the number of antenna ports is 2, the CSI-RS is transmitted in half of the specific pattern in FIG. 2, and when the number of antenna ports is 4, the CSI-RS is transmitted over the entire specific pattern, and when the number of antenna ports is 8, two patterns are used. CSI-RS is transmitted. On the other hand, muting is always done in one pattern unit. That is, muting can be applied to a plurality of patterns, but cannot be applied to only a part of one pattern when the CSI-RS and the position do not overlap. However, only when the position of the CSI-RS and the position of the muting overlap, it can be applied only to a part of one pattern.

When the CSI-RS for two antenna ports is transmitted, the CSI-RS transmits a signal of each antenna port in two REs connected in the time axis, and the signal of each antenna port is divided by an orthogonal code. In addition, when CSI-RSs for four antenna ports are transmitted, two additional REs are used in addition to CSI-RSs for two antenna ports, and signals for two additional antenna ports are transmitted in the same manner. The same is true when CSI-RSs for 8 antenna ports are transmitted.

In order to measure a downlink channel state in a cellular system, a reference signal must be transmitted. In the case of the 3GPP Long Term Evolution Advanced (LTE-A) system, the terminal measures the channel state between the base station and itself by using a CRS or CSI-RS (Channel Status Information Reference Signal) transmitted by the base station. In an embodiment, several factors should be basically considered for the channel state, which may include an amount of interference in downlink. The amount of interference in the downlink includes an interference signal and thermal noise generated by an antenna belonging to an adjacent base station, and is important for the UE to determine the downlink channel condition. For example, when a base station with one transmit antenna transmits from a base station with one receive antenna to one terminal, the terminal calculates the energy per symbol that can be received in downlink from the reference signal received from the base station and the amount of interference to be simultaneously received in the section receiving the corresponding symbol. Es/Io must be determined by judgment. The determined Es/Io is converted into a data transmission rate or a value corresponding thereto, and is notified to the base station in the form of CQI, so that the base station can determine at which data rate to transmit to the terminal in downlink.

In the case of the LTE-A system, the terminal feeds back information on the downlink channel state to the base station so that it can be utilized for downlink scheduling of the base station. That is, the terminal measures the reference signal transmitted by the base station in the downlink and feeds back the information extracted thereto to the base station in the form defined by the LTE/LTE-A standard. In LTE/LTE-A, as information fed back by the UE, there are mainly three types of information.

l RI (Rank Indicator): The number of spatial layers that the UE can receive in the current channel state

l PMI (Precoder Matrix Indicator): An indicator for the precoding matrix preferred by the UE in the current channel state

l CQI (Channel Quality Indicator): The maximum data rate that the UE can receive in the current channel state. CQI can be replaced with SINR that can be used similarly to the maximum data rate, the maximum error-correcting code rate and modulation method, and data efficiency per frequency.

The RI, PMI, and CQI are related to each other and have meaning. For example, the precoding matrix supported by LTE/LTE-A is defined differently for each rank. Therefore, the PMI value X when RI has a value of 1 and the PMI value X when RI has a value of 2 are interpreted differently. Also, when the UE determines the CQI, it is assumed that the PMI and X notified to the base station are applied by the base station. That is, the UE notifying the base station of RI_X, PMI_Y, and CQI_Z is equivalent to notifying that the data rate corresponding to CQI_Z can be received when the rank is RI_X and the precoding is PMI_Y. In this way, when the terminal calculates the CQI, it is assumed that the base station is to perform the transmission method, so that the optimized performance can be obtained when the transmission is actually performed in the corresponding transmission method.

In general, when the number of transmit antennas is large, such as in FD-MIMO, a proportional CSI-RS should be transmitted. For example, when using 8 transmit antennas in LTE/LTE-A, the base station transmits CSI-RS corresponding to 8-port to the terminal to measure the downlink channel state. In this case, in order for the base station to transmit the CSI-RS corresponding to the 8-port, radio resources composed of 8 REs as shown in A and B of FIG. 2 should be used within one RB. When such LTE/LTE-A CSI-RS transmission is applied to FD-MIMO, radio resources proportional to the number of transmission antennas should be allocated to the CSI-RS. That is, when the base station has 128 transmit antennas, the base station must transmit the CSI-RS using a total of 128 REs within one RB. Since such a CSI-RS transmission method requires excessive radio resources, it has an adverse effect of reducing radio resources required for radio data transmission/reception.

A base station having a large number of transmit antennas, such as FD-MIMO, transmits the CSI-RS using the following method.

- CSI-RS transmission method 1: A method for transmitting by allocating radio resources as many as the number of antennas to the CSI-RS

- CSI-RS transmission method 2: A method of transmitting the CSI-RS by dividing it into a plurality of dimensions

- CSI-RS transmission method 3: A method of transmitting a precoded RS by dividing the CSI-RS into a plurality of dimensions and applying precoding to each CSI-RS

CSI-RS transmission method 1 is a method of allocating CSI-RS resources as many as the number of antennas possessed by the corresponding base station to determine the state of a channel between the base station and the terminal. The method has an advantage in that information corresponding to all antennas can be accurately identified, but as the number of antennas increases, more resources are required to be allocated. In addition, as can be understood from FIG. 2 , CSI-RS resources are limited, and as the number of antennas increases, the resources for CSI-RS transmission proportionally increase, and thus overhead may increase.

FIG. 3A is a diagram illustrating CSI-RS transmission by a base station to a UE using CSI-RS transmission method 2;

Referring to FIG. 3A , a base station operating FD-MIMO according to CSI-RS transmission method 2 may be configured with a total of 32 antennas. Of these, 16 antennas (A0,…,A3, B0,…,B3, C0,…,C3, D0,…,D3) are arranged at a first angle with respect to the positive X-axis direction, and the remaining The 16 antennas E0, ..., E3, F0, ..., F3, G0, ..., G3, H0, ..., H3 may be disposed at a second angle with respect to the positive X-axis direction. In an embodiment, the first angle may be 35° to 55°, and more specifically, 45°. In addition, in an embodiment, the second angle may be -35° to -55°, and more specifically, -45°.

In this way, the antenna shape in which N/2 and the remaining N/2 of the total N antennas are arranged at an angle of 90 to each other at the same location is called XPOL. XPOL can be used to obtain a large antenna gain by placing several antennas in a small space.

In FIG. 3A, the 32 antennas of identification number 300 are A0,..,A3, B0,..,B3, C0,..,C3, D0,..,D3, E0,..,E3, F0, They are marked as ..,F3, G0,..,G3, H0,..., H3. The 32 antennas of FIG. 3A may transmit two types of CSI-RSs.

First, the H-CSI-RS for measuring the channel state in the horizontal direction may include the following 8 antenna ports.

-H-CSI-RS port 0: Consists of the transmit signal of antenna A3

-H-CSI-RS port 1: Consists of the transmit signal of antenna B3

-H-CSI-RS port 2: Consists of the transmit signal of antenna C3

-H-CSI-RS port 3: Consists of the transmit signal of antenna D3

-H-CSI-RS port 4: Consists of transmission signal of antenna E3

-H-CSI-RS port 5: Consists of the transmit signal of antenna F3

-H-CSI-RS port 6: Consists of the transmit signal of antenna G3

-H-CSI-RS port 7: Consists of the transmit signal of antenna H3

In the above description, generating one CSI-RS port by combining a plurality of antennas means antenna virtualization, and may generally be achieved through a linear combination of a plurality of antennas.

In addition, the V-CSI-RS for measuring the channel state in the vertical direction may include the following four antenna ports.

-V-CSI-RS port 0: Consists of the transmit signal of antenna A0

-V-CSI-RS port 1: Consists of the transmit signal of antenna A1

-V-CSI-RS port 2: Consists of the transmit signal of antenna A2

-V-CSI-RS port 3: Consists of the transmit signal of antenna A3

As described above, when a plurality of antennas are two-dimensionally arranged in M×N (vertical direction×horizontal direction), FD-MIMO channels are used using N horizontal CSI-RS ports and M vertical CSI-RS ports. can be measured. That is, when two types of CSI-RSs are used, channel state information can be identified by using M+N CSI-RS ports for M×N transmit antennas. As described above, using a smaller number of CSI-RS ports to obtain information on a larger number of transmit antennas has an advantage in reducing CSI-RS overhead.

As described above, when CSI-RS is transmitted using CSI-RS transmission method 2, the overhead for CSI-RS transmission and channel state information reporting is reduced compared to CSI-RS transmission method 1 for CSI-RS. Accurate channel information for an antenna to which RS is not transmitted cannot be grasped, and estimation may be required by a method such as the Kronecker product, which will be described later.

3B is a diagram illustrating a CSI-RS transmission by a base station to a UE using CSI-RS transmission method 3 according to an embodiment.

The 32 antennas of identification number 340 are transmitted as one Two-dimensional CSI-RS, and the 2D-CSI-RS, which measures the channel state of all horizontal and vertical antennas, is composed of the 32 antenna ports indicated above. can When transmitting by applying a sequence determined through a cell ID or the like to each antenna port, it corresponds to CSI-RS transmission method 1, and precoding may be applied to the sequence of transmission method 1 to transmit. This method allocates all radio resources for each antenna, thereby increasing the accuracy of channel information, but may not be effective in terms of resource efficiency by relatively using a large number of radio resources for control information or data.

Identification numbers 350 and 360 of FIG. 3B allocate a relatively small number of radio resources even if the accuracy of channel information is relatively low using the CSI-RS transmission method 3, and allow the terminal to transmit to a large number of transmission antennas. This is a method that enables channel measurement for Similar to the CSI-RS transmission method 2 described above, this is a method for transmitting the CSI-RS corresponding to the entire antenna port by dividing it into N dimensions. If there is, the CSI-RS is transmitted by dividing it into two dimensions. At this time, one CSI-RS is operated as a Horizontal CSI-RS that measures channel information in the horizontal direction, and the other CSI-RS is operated as a Vertical CSI-RS that measures channel information in the vertical direction. However, the difference from the above CSI-RS transmission method 2 is that in the case of CSI-RS transmission method 2, if only a signal corresponding to one antenna port is included in one CSI-RS, in the case of CSI-RS transmission method 3, one Signals corresponding to a plurality of antenna ports are included in the CSI-RS. When the relationship between the plurality of antenna ports is combined by precoding corresponding to the horizontal or vertical direction corresponding to the antenna and transmitted through one CSI-RS transmission resource, the terminal transmits the plurality of antennas to the corresponding CSI-RS. information can be obtained at once. At this time, the H-CSI-RS for measuring the channel state in the horizontal direction is composed of the following 8 antenna ports.

- H-CSI-RS port 0: Antennas A0, A1, A2, A3 are combined

- H-CSI-RS port 1: Antenna B0, B1, B2, B3 are combined

- H-CSI-RS port 2: Antennas C0, C1, C2, C3 are combined

- H-CSI-RS port 3: Antenna D0, D1, D2, D3 are combined

- H-CSI-RS port 4: Antennas E0, E1, E2, E3 are combined

- H-CSI-RS port 5: Antenna F0, F1, F2, F3 are combined

- H-CSI-RS port 6: Antenna G0, G1, G2, G3 are combined

- H-CSI-RS port 7: Antennas H0, H1, H2, H3 are combined

In the above description, generating one CSI-RS port by combining a plurality of antennas means antenna virtualization, and is generally performed through a linear combination of a plurality of antennas. In addition, the V-CSI-RS for measuring the channel state in the vertical direction is composed of the following four antenna ports.

- V-CSI-RS port 0: Antennas A0, B0, C0, D0, E0, F0, G0, H0 are combined

- V-CSI-RS port 1: Antennas A1, B1, C1, D1, E1, F1, G1, H1 are combined

- V-CSI-RS port 2: Antennas A2, B2, C2, D2, E2, F2, G2, H2 are combined

- V-CSI-RS port 3: Antennas A3, B3, C3, D3, E3, F3, G3, H3 are combined

As described above, when a plurality of antennas are two-dimensionally arranged in M×N (vertical direction×horizontal direction), FD-MIMO channels are used using N horizontal CSI-RS ports and M vertical CSI-RS ports. can be measured. That is, when two CSI-RSs are used, channel state information can be identified by using M+N CSI-RS ports for M×N transmit antennas. As described above, using a smaller number of CSI-RS ports to identify information on a larger number of transmit antennas can reduce CSI-RS overhead. Precoding for combining a plurality of antennas into one CSI-RS port is determined through cell ID or CSI-RS RNTI, symbol index, subframe index, frame index, etc. It can also be a sequence. In FIGS. 3A and 3B, 32 transmit antennas are allocated to 8 H-CSI-RS ports and 4 V-CSI-RS ports and transmitted, thereby allowing the UE to measure the radio channel of the FD-MIMO system. In the above, H-CSI-RS allows the terminal to measure information on the horizontal angle between the terminal and the base station transmission antenna as in identification numbers 320 and 360, whereas in the V-CSI-RS, the terminal and the terminal as in identification numbers 330 and 370, It is possible to measure information about the vertical angle between the base station's transmit antennas.

The following abbreviations may be used to describe the embodiments of the present specification.

- RI _H : A rank indicator in which the UE notifies the base station of the rank of a channel obtained by applying vertical precoding to 2D-CSI-RS or a channel obtained by measuring horizontal CSI-RS (H-CSI-RS)

- RI _V : A rank indicator in which the UE notifies the base station of the rank of a channel obtained by applying horizontal precoding to 2D-CSI-RS or a channel obtained by measuring vertical CSI-RS (V-CSI-RS)

- PMI _H : Based on a channel obtained by applying vertical precoding to 2D-CSI-RS or a channel obtained by measuring horizontal CSI-RS (H-CSI-RS), the terminal obtains an optimal precoding precoding matrix indicator notified to

- PMI _V : Based on the channel obtained by applying horizontal precoding to 2D-CSI-RS or the channel obtained by measuring CSI-RS (V-CSI-RS) in the vertical direction, the terminal obtains the optimal precoding precoding matrix indicator notified to

- CQI _H : Data rate supported by the terminal generated under the assumption that only horizontal precoding is applied

- CQI _V : Data rate supported by the terminal generated under the assumption that only vertical precoding is applied

- CQI _HV : A data rate that can be supported by a terminal generated under the assumption that horizontal and vertical precoding are applied simultaneously

In the embodiment of the present specification, horizontal channel state information and horizontal channel state information are described, but in other embodiments, it may also be described in general terms such as channel state information 1 and channel state information 2 .

Based on the 2D-CSI-RS or the plurality of CSI-RSs transmitted as shown in FIG. 3, the UE may notify the base station of the radio channel of the FD-MIMO system by transmitting RI, PMI, and CQI to the base station.

4 is a diagram illustrating that the UE transmits RI, PMI, and CQI for 2D-CSI-RS.

Referring to FIG. 4 , arrows in the drawing indicate how one type of channel state information is related to interpretation of another type of channel state information.

That is, the arrow starting at _{RI V} 400 and ending at _{PMI V} 410 means that the interpretation of _{PMI V} varies according to the value of _{RI V 400 .}

In FIG. 4, the UE measures 2D-CSI-RS and transmits channel state information such as feedback 1 to the base station. In addition, the terminal obtains channel information corresponding to the horizontal using the information on the optimal vertical precoding obtained at this time, obtains the _{same rank as the RI H} (430), and then obtains the optimal precoding PMI _H (440) corresponding to the horizontal direction. , and then transmits channel state information such as feedback 2 including the _{CQI H 450 to the base station.}

In an embodiment, at least two of RI, PMI, and CQI may be transmitted with correlation with each other. That is, in the case of feedback 1, the RI _V (400) indicates _{which rank the PMI V} (410) transmitted later indicates the precoding matrix. In addition, CQI _V 420 is when the base station transmits a signal to the terminal in the rank designated by the _{RI V} 400, the terminal receives the signal when the precoding matrix of the corresponding rank designated by the _{PMI V 410 is applied to the signal transmission} Possible data rates or corresponding information may be included.

In the case of Feedback 2 in the embodiment, like feedback 1, at least two values of RI, PMI, and CQI are transmitted with correlation with each other.

5 is a diagram illustrating that the UE transmits RI, PMI, and CQI for a plurality of CSI-RSs according to an embodiment.

Referring to FIG. 5 , the UE measures V-CSI-RS and transmits channel state information such as feedback 1 to the base station. In addition, the terminal measures the H-CSI-RS and transmits channel state information such as feedback 2 to the base station.

In an embodiment, RI, PMI, and CQI may be transmitted with correlation with each other. That is, in the case of feedback 1, the RI _V 500 may indicate _{which rank the PMI V} 510 transmitted later indicates the precoding matrix. In addition, when the CQI _V 520 applies the precoding matrix of the corresponding rank designated by the _{PMI V} 510 when the base station transmits a signal to the terminal in the rank designated by the _{RI V 500, the data rate that the terminal can receive} Or it may include information corresponding thereto.

In the case of Feedback 2, like feedback 1, RI, PMI, and CQI are transmitted with correlation with each other.

As shown in FIGS. 4 and 5, setting 2D-CSI-RS or a plurality of feedbacks for a plurality of transmit antennas of the FD-MIMO base station so that the terminal reports the channel state information to the base station is one of the methods for FD-MIMO. It may be a method of reporting channel state information. Such a method has an advantage that no additional implementation is required to generate and report channel state information for FD-MIMO in the UE. On the other hand, if the channel state information reporting method of the method shown in FIG. 4 is used, there is a disadvantage in that the performance of the FD-MIMO system cannot be sufficiently obtained. The reason that the performance of the FD-MIMO system cannot be sufficiently obtained is that, as shown in FIG. 4, 2D-CSI-RS or a plurality of feedbacks are set so that the UE reports the channel state information to the base station only when FD-MIMO is applied. This is because the terminal does not upload the CQI assuming the precoding of .

In the FD-MIMO system, when a plurality of transmission antennas are arranged in two dimensions as shown in FIG. 3, both vertical and horizontal precoding of a signal transmitted to the terminal is applied and transmitted. That is, the terminal does not receive a signal to which only one of the precodings corresponding to _{PMI H} and PMI _V of FIGS. 4 and 5 is applied, but a signal to which the precoding corresponding to _{PMI H} and PMI _{V is simultaneously applied.}

As in FIGS. 4 and 5, _{when only CQI H} and CQI _V when precoding corresponding to _{PMI H} and PMI _V are separately applied to the base station, the base station sends the CQI when precoding is applied in both vertical and horizontal directions to the terminal You don't get it and you have to judge for yourself. As described above, if the base station arbitrarily determines the CQI determination when both vertical and horizontal precoding are applied based on CQIs when vertical and horizontal precoding is applied, it may act as a cause of degrading system performance.

It is necessary to define how to determine the CQI when a plurality of precodings are applied. When calculating the CQI when only one precoding is applied, the UE calculates the CQI on the assumption that the precoding specified by the RI and PMI notified by the UE is applied to the downlink. However, in the _{case of the CQI HV} , the UE may calculate the CQI on the assumption that two precodings are simultaneously applied to the downlink. At this time, the terminal can interpret that two precodings are applied at the same time in various ways, and the Kronecker product can be one of such interpretation methods. The Kronecker product is defined for two matrices as follows.

In Equation 1, A and B are _{replaced with precoding matrices designated by PMI H} and PMI _V , respectively, so that precoding when two precodings are simultaneously applied can be obtained. When calculating the _{CQI HV} 550 , the UE may calculate the CQI assuming that precoding obtained by applying the _{above equation to the precoding matrix specified by PMI H} and PMI _{V is applied to the downlink.}

In order to obtain precoding when two precodings are simultaneously applied using the Kronecker product of Equation 1, different operations are required for the terminal and the base station according to the rank notified by the terminal.

The MIMO system can be divided into a closed-loop MIMO system and an open-loop MIMO system according to whether PMI information on the receiver side is used when forming a transmission beam pattern.

In the case of a closed-loop MIMO system, the UE uses CSI-RS to identify channel information, obtains the rank of the corresponding channel through this, and informs the base station through RI. In addition, the UE may select an optimal precoding from among the precoder sets corresponding to the determined rank and transmit the PMI corresponding to the selected precoding to the base station. In addition, the terminal feeds back a data rate that the terminal can support to the base station through CQI based on the current channel obtained on the assumption that the optimal precoding is applied. The base station receiving such feedback designates the terminal to communicate using appropriate transmission/reception precoding based on the corresponding information.

On the other hand, in the case of the open-loop MIMO system, the receiver does not transmit PMI information to the transmitter, unlike the closed-loop MIMO system. Instead, the receiver of the open-loop MIMO system assumes the method specified in the standard as the precoding to be assumed for the time and frequency space when generating the CQI according to time and frequency resources, or a precoding set by higher-level signaling to determine the supportable data rate. and transmits it to the transmitter through CQI. The transmitter, having received the CQI from the receiver, determines how the terminal should communicate based on the corresponding information.

In general, it is known that closed-loop MIMO exhibits greater system performance than open-loop MIMO because channel information can be adaptively used. In the case of closed-loop MIMO, there is a process in which the terminal selects the preferred precoding and notifies the base station, whereas in the case of open-loop MIMO, this process does not exist. because it is However, in order to transmit/receive a signal through closed-loop MIMO, an additional overhead such as a UE transmitting a PMI to a base station is required. In addition, when transmitting and receiving signals using closed-loop MIMO, the beam pattern of the interference signal changes rapidly with time in a situation where the mobile speed of the terminal is very fast or the channel changes abruptly, so performance loss due to the change of the interference signal may occur. there is. Such interference is called dynamic interference.

On the other hand, in the case of an open-loop MIMO system, the performance efficiency of the system itself is lower than that of a closed-loop MIMO system, but there are advantages such as less influence of dynamic interference and less feedback overhead for PMI. Such feedback overhead for PMI becomes particularly important in FD-MIMO in which the number of antennas of a base station increases. This is because as the number of transmit antennas of the base station increases, the number of bits constituting the PMI for notifying the preferred precoding of the terminal must increase.

In the embodiment of the present specification, in the case of precoding corresponding to open-loop MIMO, it can be assumed that the base station and the terminal share information related to the rank as well as the precoding designation. Accordingly, the terminal notifies the base station of the RI for the channel corresponding to the closed-loop MIMO through the uplink control signal, and the base station can determine the rank of the corresponding precoding through this.

As mentioned above, the CSI-RS in the FD-MIMO system can be operated in various ways. The method of operating the CSI-RS is a method of allocating a CSI-RS to all antennas and allowing the UE to measure a plurality of CSI-RSs capable of effectively measuring a large number of transmit antennas in order to reduce the use of radio resources. include

When 2D-CSI-RS is allocated to all antennas, 2D-CSI-RS can create a 1D channel by applying 1D precoding to a channel having a plurality of dimensions. When a plurality of CSI-RSs are measured by the UE, each CSI-RS may be utilized for the UE to measure a channel state for one of a plurality of dimensions for measuring one radio channel. This requires relatively few radio resources for CSI-RS transmission compared to allocating a unique CSI-RS port for each transmission antenna.

For example, by operating two CSI-RSs in the vertical and horizontal directions for the transmit antenna of the FD-MIMO system arranged in a rectangle, effective channel state measurement is possible for the UE.

In the embodiment of the present specification, each CSI-RS is one of a closed-loop MIMO and an open-loop MIMO system in a system such as FD-MIMO having a plurality of transmit antennas and operating 2D-CSI-RS or a plurality of CSI-RSs. We propose to selectively operate the above.

In addition, in the technology and apparatus using the Hybrid MIMO system proposed in the embodiment of the present specification, when the channel state measurement method using 2D-CSI-RS or a plurality of CSI-RSs is performed so that the terminal effectively measures radio channel state information , a 1D channel created based on 2D-CSI-RS or a 1D channel derived based on some of a plurality of CSI-RSs is operated using a predetermined PMI to operate as an open-loop MIMO system, and the remaining CSI-RSs are closed In order to operate as a loop MIMO system, an optimal PMI is found and transmitted to the base station through an uplink control channel. _{In addition, CQI HV} indicating a terminal supportable data rate generated on the assumption that a predetermined precoding corresponding to an open-loop MIMO system and an optimal precoding corresponding to a closed-loop MIMO system are simultaneously applied. It can also be transmitted to the base station through an uplink control channel. Throughout this specification, such a MIMO transmission/reception method may be referred to as Hybrid MIMO.

In a system such as FD-MIMO that operates 2D-CSI-RS or a plurality of CSI-RSs and supports a Hybrid MIMO system, whether each CSI-RS operates in an open loop or a closed loop is determined by one or more of the following methods can be used to notify the base station to the terminal.

- CSI-RS definition method operating as an open-loop MIMO system 1: When the number of CSI-RS ports in one dimension in 2D-CSI-RS is 1, the dimension (vertical or horizontal) corresponding to the CSI-RS is open-loop works with Depending on the embodiment, the number of ports of the CSI-RS may vary, but when the number of specific CSI-RSs is a preset value, a feedback method of a dimension corresponding to the CSI-RS may be determined.

- CSI-RS definition method operating in an open-loop MIMO system 2: If PMI/RI reporting is not configured in the CSI-RS, the dimension (vertical or horizontal) corresponding to the CSI-RS operates as an open-loop .

- CSI-RS definition method operating as an open-loop MIMO system 3: Whether to operate in an open or closed loop in the corresponding CSI-RS is set using higher-order signaling, and an open loop or a closed loop is configured according to the configuration. It works.

In the case of CSI-RS definition method 2 operating as an open-loop MIMO system, the current Rel. 10 In the case of transmission modes 8, 9, and 10 in the LTE system, the base station can set a mode that operates without transmitting PMI and RI. It can be set to operate as a loop system.

As mentioned above, in the communication system using the Hybrid MIMO system, the UE feeds back only the RI and CQI to the base station for precoding in the state of operating as the open-loop MIMO system. A method of defining precoding operating in an open-loop MIMO system may include one or more of the following methods.

- Precoding definition method that operates as an open-loop MIMO system 1: One precoding is defined according to time and frequency resources.

- Precoding definition method that operates in an open-loop MIMO system 2: Defines a plurality of precodings as a set according to time and frequency resources.

Basically, precoding definition methods 1 and 2 operating in an open-loop MIMO system operate by transmitting _{CQI HV} indicating a data rate that can be supported by a terminal generated on the assumption that precoding operating in a closed-loop MIMO and an open-loop MIMO system is simultaneously applied. things are the same However, the terminal can support data transmission CQI _{HV CQI HV} according to the optimal precoding derivation method applied to The procedure for determining the open-loop precoding used for

In an embodiment, when operating according to precoding definition method 1 operating as an open-loop MIMO system, precoding may be defined according to time and frequency resources as follows.

- Method of defining one precoding according to resource 1: _{Allocating precoding corresponding to PMI H} as open-loop MIMO and defining according to time and frequency resources.

- Method of defining one precoding according to resource 2: _{Allocating precoding corresponding to PMI V} as open-loop MIMO and defining according to time and frequency resources.

6 is a diagram illustrating that precoding corresponding to PMIH is allocated as open-loop MIMO and defined according to time and frequency resources according to an embodiment. _{More specifically, when the precoding corresponding to PMI H} (640, 690) used in time and frequency resources is defined by the open-loop MIMO system assumption according to method 1 of defining one precoding according to the resource, the UE assumes this assumption _{It is exemplified that PMI V} (610, 660) corresponding to the closed-loop MIMO system assumption _{and CQI HV} (620, 670), which is the maximum data rate of the composite channel, are transmitted to the base station.

In FIG. 6, UE Feedback means information included in a signal that the terminal transmits to the base station, and Assumption means information that the terminal does not transmit to the base station but is mutually recognized by the base station and the terminal according to a predefined definition. will be.

It is assumed in FIG. 6 that the UE is receiving a 2D-CSI-RS or two CSI-RSs (V-CSI-RS and H-CSI-RS). 2D-CSI-RS is a CSI-RS that transmits by allocating radio resources to all antennas, and V-CSI-RS and H-CSI-RS are transmitted to provide different information about the two-dimensional antenna array constituting FD-MIMO. CSI-RS. The technique proposed in the embodiment of the present specification may include a process in which the terminal generates channel state information for a two-dimensional antenna array using a 2D-CSI-RS or a plurality of CSI-RSs and notifies the terminal to the base station.

In an embodiment, the terminal generates channel state information in the vertical direction (600, 610, 620, etc.) and notifies the base station, but the channel state information in the horizontal direction may be separately generated or not notified to the base station.

The terminal may not separately generate channel state information in the horizontal direction. In an embodiment, the terminal may determine the channel state information in the horizontal direction based on information notified by the base station through upper signaling to the terminal or a rule promised to the base station and the terminal.

As an example, the terminal does not generate a PMI in the horizontal direction and does not notify the base station of this. Instead, the terminal assumes _{that the vertical precoding designated by the PMI V} 610 notified to the base station and the precoding 640 preset by the base station are applied in the horizontal direction and can determine _{the CQI HV 620 accordingly.} there is.

In an embodiment, the terminal obtains the rank of a channel obtained by measuring a vertical channel obtained by applying a predetermined horizontal precoding or a vertical CSI-RS (V-CSI-RS), and the obtained rank information is transmitted to the base station Notice through RI _V (600).

_{In an embodiment, the RI H} 630, which is the rank of the channel for the CSI-RS (H-CSI-RS) in the horizontal direction, is shared between the base station and the terminal through some higher signaling, or the terminal and the base station It can be assumed that there is a predefined definition between

After the RI _V (600) notification, the UE derives and uses two channel state information based on the 2D-CSI-RS or two CSI-RSs as shown in FIGS. 4 and 5 to determine the optimal precoding. can _{The UE uses precoding and RI V corresponding to RI H} (630) and PMI _H (0) (640) defined in advance in an open-loop MIMO system through a channel combined based on 2D-CSI-RS or a plurality of CSI-RSs. Based on the result derived by combining possible precodings corresponding to (600), the optimal precoding is _{transmitted through the PMI V} (610). can do. In an embodiment, the base station may _{identify PMI H} (0).

_{At this time, the PMI H} (0) 640 corresponding to the precoding that is promised in advance operating as an open-loop MIMO system is not notified through the upper link control channel, whereas in the case of CQI indicating the maximum data rate, a predefined Assuming the PMI _{H (0) 640 and the PMI V} 610 derived through the CSI-RS, the _{maximum data rate CQI HV} 620 obtained through the derived channel is notified to the base station. In the embodiment, a case in which the precoding in the horizontal direction assumed by the terminal changes according to the change of the time resource is illustrated. As described above, in addition to the case where the precoding assumed by the terminal varies according to the time resource, it is also possible that the precoding assumed by the terminal varies according to the frequency resource.

For the next time and frequency resource, the terminal notifies the _{base station of the RI V} 650 as in the previous time and frequency resource, and the _{RI H} 680 is shared with each other through some higher signaling like the previous time and frequency resource. or it is assumed to have been defined in advance. Based on the results obtained by combining precodings corresponding to RI _H (680) and PMI _H (1) (690) and _{possible precodings corresponding to RI V} (650), the optimal precoding is determined by PMI _V (660) transmitted through

_{At this time, the terminal does not notify the PMI H} (1) 690 corresponding to the precoding promised in advance for the next time and frequency resource through the upper link control channel, as in the identification number 630, and does not notify the PMI defined in advance. _{Assuming H (1) 690 and PMI V} 660 derived through CSI-RS, the _{maximum data rate CQI HV} 670 obtained through the derived channel is notified to the base station.

7 is a diagram illustrating _{that precoding corresponding to PMI V} is allocated as open-loop MIMO and defined according to time and frequency resources according to an embodiment. _{More specifically, FIG. 7 shows a terminal when precoding corresponding to PMI V} (740, 790) used in time and frequency resources is defined by an open-loop MIMO system assumption according to method 2 of defining one precoding according to a resource. Under these assumptions, each optimal precoding _{and, accordingly, PMI H} (710, 760) corresponding to the closed-loop MIMO system assumption _{and CQI HV} (720, 770), which is the maximum data rate of the composite channel, are transmitted to the base station.

In the embodiment, like FIG. 6 , UE Feedback means signals that the terminal transmits to the base station, and Assumption means a signal that the terminal does not transmit to the base station but is mutually recognized by the base station and the terminal according to a predefined definition. there is.

In FIG. 7, in contrast to FIG. 6, the UE obtains the rank of a channel obtained by applying vertical precoding to 2D-CSI-RS or a channel obtained by measuring horizontal CSI-RS (H-CSI-RS), and sends it to the base station. It can notify the base station through the RI _{H (700). The RI V} 730, which is the rank of the channel for the vertical CSI-RS (V-CSI-RS), is shared between the base station and the terminal through some higher signaling, or between the base station and the terminal in advance. It can be assumed that it is defined in

After the RI _H 700 notification, the UE derives and combines two channel state information based on the 2D-CSI-RS or two CSI-RSs as shown in FIGS. 4 to 6 above to determine the optimal precoding. do.

_{The UE performs precoding and RI H corresponding to RI V} 730 and PMI _V (0) 740 defined in advance in an open-loop MIMO system through a channel combined based on 2D-CSI-RS or a plurality of CSI-RSs. Based on the result derived by combining possible precodings corresponding to 700 , the optimal precoding may be transmitted to the base station through the _{PMI H 710 .}

_{At this time, the terminal does not notify the base station of the PMI V} (0) 740 corresponding to the precoding promised in advance operating as an open-loop MIMO system through the upper link control channel, whereas the terminal indicates the maximum data rate. In the case of CQI, the maximum data rate obtained through the channel derived by assuming the _{predefined PMI V} (0) 740 and the PMI _H 710 derived through CSI-RS is notified to the base station through _{CQI HV 720} can do.

For the next time and frequency resource, the terminal notifies the _{base station of the RI H} 750 as in the previous time and frequency resource, and the _{RI V} 780 is shared with each other through some higher signaling like the previous time and frequency resource. or it can be assumed that it is defined in advance. Based on the results obtained by combining the precodings corresponding to the predefined RI _V (780) and PMI _V (1) (790) and _{the possible precodings corresponding to the PMI H} (760), the optimal precoding is determined by PMI _H (760) can be transmitted through

At this time, the terminal does not notify the base station through the upper link control channel of _{the PMI V} (1) 790, which corresponds to the precoding promised in advance for the next time and frequency resource, as in the identification number 730, and does not Assuming the PMI _{V (1) 790 and the PMI H} 760 derived through the CSI-RS, the _{maximum data rate CQI HV} 770 obtained through the derived channel is notified to the base station.

When operating according to precoding definition method 2 operating as an open-loop MIMO system, a set of a plurality of precodings is defined by the assumption of an open-loop MIMO system according to time and frequency resources based on 2D-CSI-RS or a plurality of CSI-RSs. It can be assumed that there is

At this time, the terminal obtains one optimal precoding set from among these pre-defined plurality of precoding sets, and {PMI _H , PMI _V } _{One PMI and one CQI HV} corresponding to the closed-loop MIMO system assumption are transmitted to the base station. In precoding definition method 2 operating as an open-loop MIMO system, the UE selects PMIs corresponding to one optimal precoding set from among a plurality of precoding sets defined as follows and delivers one of them to the base station. The base station may operate as a Hybrid MIMO system in which one PMI is notified from the terminal and precoding corresponding to the entire set is inferred from the notified PMI.

- Method of defining the precoding set according to resource 1: RI _V and PMI _V are delivered to the base station.

- Method of defining the precoding set according to the resource 2: RI _H and PMI _H are transmitted to the base station.

_{8 is a diagram illustrating that a UE transmits RI V} and PMI _V to a base station according to method 1 of defining a precoding set according to a resource according to an embodiment.

Referring to FIG. 8 , UE Feedback means signals that the terminal transmits to the base station, and Assumption means a signal that the terminal does not transmit to the base station but is mutually recognized by the base station and the terminal according to a predefined definition. .

_{In the embodiment, it is assumed that the RI V} 830, which is the rank of the channel for the vertical CSI-RS (V-CSI-RS), is shared with each other through some higher signaling or is predefined. 6 to 7, the UE _{uses a channel obtained by using a precoding set corresponding to the precoding corresponding to the defined RI V} (830, 880) or CSI-RS in the horizontal direction (H-CSI-RS) Calculate the rank of the channel obtained by measuring , and _{notify the base station through RI H} (800). After the RI _H 800 is notified, the UE derives and combines two channel state information based on the 2D-CSI-RS or two CSI-RSs as described above for PMI derivation.

In an embodiment, the UE selects a set of precodings corresponding to _{RI V} (830) and RI _H (800) predefined in an open-loop MIMO system through a channel combined based on 2D-CSI-RS or a plurality of CSI-RSs. The precoding set showing the best performance considering {PMI _H , PMI _V (2)} to derive (identification number 840). The terminal transmits the precoding corresponding to the H-CSI-RS among the derived results to the base station through the _{PMI H 810 .} In addition, in the case of CQI indicating the maximum data rate, the terminal assumes the optimal precoding set {PMI _H , PMI _{V (2)} determined through the channel state, and the maximum data rate CQI HV} 820 obtained through the derived channel is the base station. will be notified to

The base station checks the rank of each precoding through _{the RI H} 800 and the predefined RI _V 830 transmitted by the terminal in this way, and the corresponding time and frequency resource through the _{received PMI H 810.} You can check the precoding set {PMI _H , PMI _V (2)}. Using this information, it is confirmed that the received maximum data rate CQI _HV 820 is created assuming the precoding set {PMI _H , PMI _{V (2)}.}

_{For the next time and frequency resources, the UE also shares the RI V} 880, which is the rank of the channel for the vertical CSI-RS (V-CSI-RS), between the base station and the UE through some higher signaling, and Or, it is assumed that it is defined in advance between the base station and the terminal.

After the UE notifies the RI _H 880, the UE may derive and combine two pieces of channel state information based on the two CSI-RSs as described above for PMI derivation. The UE considers a set of precodings corresponding to _{RI V} (880) and RI _H (850) defined in advance in an open-loop MIMO system through a channel combined based on a plurality of CSI-RSs, and a precoding set showing optimal performance {PMI _H , PMI _V (5)} (890) to derive The terminal may transmit the information corresponding to the derived result to the base station through the _{PMI H 860 for precoding corresponding to the H-CSI-RS.}

In the case of CQI indicating the maximum data rate, the terminal assumes the optimal precoding set {PMI _H , PMI _{V (5)} determined through the channel state, and the maximum data rate CQI HV} (870) obtained through the derived channel. The base station is notified.

The base station checks the rank of each precoding through _{the RI H} 850 and the predefined RI _V 880 transmitted by the terminal as described above, and corresponds to the corresponding time and frequency resource through the _{received PMI H 860.} Check the precoding set {PMI _H , PMI _V (5)}. The base station uses this information to _{confirm that the received maximum data rate CQI HV} 880 is created assuming the precoding set {PMI _H , PMI _V (5)}.

_{9 is a diagram illustrating that a UE transmits RI V} and PMI _V to a base station using method 2 of defining a precoding set according to a resource according to an embodiment.

Referring to FIG. 9 , UE Feedback means signals that the terminal transmits to the base station, and Assumption means a signal that the terminal does not transmit to the base station but is mutually recognized by the base station and the terminal according to a predefined definition.

_{In an embodiment, the RI H} 930, which is the rank of the channel for the CSI-RS (H-CSI-RS) in the horizontal direction, is shared between the terminal and the base station through some higher signaling, or the terminal and the base station It is assumed that there is a predefined definition between The UE obtains the rank of a channel obtained by measuring a channel obtained by applying a predefined horizontal precoding to the 2D-CSI-RS or a CSI-RS (V-CSI-RS) in the vertical direction, and sends the RI _H ( 900) to notify you. After the RI _V 900 is notified, the UE derives and combines two pieces of channel state information based on two CSI-RSs as described above for PMI derivation.

The UE considers a set of precodings corresponding to _{RI H} (930) and RI _V (900) predefined in an open-loop MIMO system through a channel combined based on 2D-CSI-RS or a plurality of CSI-RSs. The precoding set showing the performance of {PMI _H (1), PMI _V }(940) to derive

In an embodiment, the terminal transmits the precoding corresponding to the V-CSI-RS among the derived results to the base station through the _{PMI V 910 .} In the case of CQI indicating the maximum data rate, the terminal assumes the optimal precoding set {PMI _H (1), PMI _{V } (940) determined through the channel state, and the maximum data rate CQI HV} (920) obtained through the derived channel. to the base station through

The base station checks the rank of each precoding through _{the RI V} 900 and the predefined RI _H 930 transmitted by the UE as described above, and corresponds to the corresponding time and frequency resource through the _{received PMI V 910} You can check the precoding set {PMI _H (1), PMI _V } (910). The base station uses this information to _{confirm that the received maximum data rate CQI HV} 920 is created assuming the precoding set {PMI _H (1), PMI _V } 940).

_{For the next time and frequency resource, the UE shares the RI H} 980, which is the rank of the channel for the horizontal CSI-RS (H-CSI-RS), between the base station and the UE through some higher signaling, or , it is assumed that it is defined in advance between the base station and the terminal.

After the RI _V 950 is notified, the UE may derive and combine two pieces of channel state information based on the 2D-CSI-RS or two CSI-RSs as described above for PMI derivation.

In an embodiment, the UE selects a set of precodings corresponding to _{RI H} 980 and RI _V 950 defined in advance in an open-loop MIMO system through a channel combined based on 2D-CSI-RS or a plurality of CSI-RSs. Considering that, the precoding set showing the optimal performance {PMI _H (0), PMI _V }(990) to derive The terminal transmits the precoding corresponding to V-CSI-RS among the derived results to the base station through the _{PMI V 960 .} In the embodiment, in the case of CQI indicating the maximum data rate, the terminal assumes the optimal precoding set {PMI _H (0), PMI _{V } (990) determined through the channel state, and the maximum data rate CQI HV} obtained through the derived channel 970 is notified to the base station.

The base station checks the rank of each precoding through _{the RI V} 950 and the predefined RI _H 980 transmitted by the terminal as described above, and corresponds to the corresponding time and frequency resource through the _{received PMI V 960} Check the precoding set {PMI _H (0), PMI _V }(990).

Using this information, the base station _{confirms that the received maximum data rate CQI HV} 980 is created assuming the precoding set {PMI _H (0), PMI _V } (990).

In an embodiment, in order to operate in such an open-loop MIMO system, it is necessary to pre-determine precoding in which the base station and the terminal operate according to time and frequency resources. The precoding definition method according to these resources is as follows.

- Precoding definition method according to time and frequency resources 1: Definition for each subband.

- Precoding definition method according to time and frequency resources 2: Defined for each wideband.

When defining for each subband as in Method 1 of defining precoding according to time and frequency resources, it can be defined for each subband as follows.

- Precoding definition method for each subband 1: Define PMI _H in advance.

- Precoding definition method for each subband 2: Define PMI _V in advance.

- Precoding definition method for each subband 3: PMI _H and PMI _V are defined in advance for each terminal.

- Precoding definition method for each subband 4: Define PMI _V and PMI _H in advance for each terminal.

- Precoding definition method for each subband 5: Define a plurality of PMI sets {PMI _H , PMI _V } in advance.

10 illustrates an example in which a base station and two terminals assume precoding definition method 1 for each subband according to an embodiment.

_{Referring to FIG. 10 , PMI H} may be defined in advance through precoding definition method 1 for each subband.

If it is assumed that a PMI of 4 bit width is used in the embodiment, _{precoding corresponding to PMI H} (0), ..., PMI _H (15) may be defined in advance according to time and frequency resources as shown in FIG. 10 . can Hybrid MIMO can be operated by using method 1 in _{which PMI H} and one precoding defined as above are defined according to resources. Allocation according to user, time, and frequency resource may be allocated using at least one of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal. Although it is assumed that a PMI having a width of 4 bits is used for convenience of explanation throughout the embodiments, it is obvious that a PMI having a width other than that may be used.

At this time, when assigning precoding to other terminals using adjacent time and frequency resources, such as identification number 1000 and identification number 1010, it can be designed to minimize the amount of signal interference that each terminal gives to the other terminal. there is. In addition, in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE, it is assumed that one terminal communicates. Likewise, it is necessary to allocate precoding for multiple users.

The above example exemplifies that two terminals _{communicate with open-loop MIMO using the PMI H} promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

11 illustrates an example in which a base station and two terminals assume precoding definition method 2 for each subband according to an embodiment.

_{Referring to FIG. 11 , PMI V} may be defined in advance through precoding definition method 2 for each subband. Assuming that a 4-bit width PMI is used _{, precoding corresponding to PMI V} (0), ... , PMI _V (15) may be defined in advance according to time and frequency resources as shown in FIG. 11 . Hybrid MIMO communication can be used by using method 2 in _{which PMI V} defined as above and one precoding are defined according to resources. Allocation according to user, time, and frequency resource may be allocated using at least one of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal.

At this time, when assigning precoding to other terminals using adjacent time and frequency resources, such as identification number 1100 and identification number 1110, it should be designed to minimize the amount of signal interference that each terminal gives to the other terminal. . In addition, although it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in the existing LTE, in order to support multiple users in a hybrid MIMO situation as in the above example, as shown in FIG. 11 It is necessary to allocate precoding for multiple users as shown.

The above example exemplifies that two terminals _{communicate with open-loop MIMO using the PMI H} promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

12 illustrates an example in which a base station and two terminals assume a predcoding definition method 3 for each subband according to an embodiment.

_{12, PMI H} through subband-specific precoding definition method 3 and PMI _V can be defined in advance. Assuming that a 4-bit width PMI is used _{, the precoding corresponding to PMI H} (0), ..., PMI _H (15), PMI _V (0), ..., PMI _V (15) is shown in the above diagram. 12, it can be defined in advance according to time and frequency resources. Hybrid MIMO communication can be used by using methods 1 and 2 for _{defining PMI H} and PMI _V defined as above and one precoding according to resources for each terminal. As in definition methods 1 and 2, allocation according to user, time, and frequency resources can be allocated using various values such as subband index, subframe index, C-RNTI mod N, and cell id possessed by the terminal.

In case of subband-specific precoding definition method 3, UE0 uses PMI _H as an open-loop MIMO system, and UE1 uses PMI _V as an open-loop MIMO system to minimize interference between precodings assigned to each other. Also, as before, it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE. 12, it is necessary to allocate precoding to multiple users. _{The above example exemplifies that two terminals communicate with open-loop MIMO by using PMI H} and PMI _V and , which are promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

13 illustrates an example in which a base station and two terminals assume a precoding definition method 4 for each subband according to an embodiment.

_{Referring to FIG. 13, PMI V} through precoding definition method 4 for each subband and PMI _H may be defined in advance. Assuming that a 4-bit width PMI is used _{, the precoding corresponding to PMI H} (0), ..., PMI _H (15), PMI _V (0), ..., PMI _V (15) is shown in FIG. 13 can be defined in advance according to time and frequency resources. Hybrid MIMO communication can be used by using methods 1 and 2 for _{defining PMI H} and PMI _V defined as above and one precoding according to resources for each terminal. As in definition methods 1 and 2, allocation according to user, time, and frequency resources can be allocated using various values such as subband index, subframe index, C-RNTI mod N, and cell id possessed by the terminal. In case of subband-specific precoding definition method 4, UE0 uses PMI _V as an open-loop MIMO system, and UE1 uses PMI _H as an open-loop MIMO system to minimize interference between precodings assigned to each other. Also, as before, it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE. 13, it is necessary to allocate precoding for multiple users. _{The above example exemplifies that two terminals communicate with open-loop MIMO using PMI H} and PMI _V and , which are promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

14 illustrates an example of defining time and frequency resources for defining _{a plurality of precoding sets {PMI H} , PMI _V } in advance using the precoding definition method 5 for each subband according to an embodiment.

Referring to FIG. 14, when time and frequency resources are allocated to apply precoding definition method 3 for each subband, a precoding set {PMI _H , PMI _V } can be defined for each time and frequency resource as shown in Table 1 below. .

Table 1 below shows the definition of the _{precoding set {PMI H} , PMI _{V } for each subband.}

Table 1 above defines in advance the number of cases for _{a set of possible precodings {PMI H} , PMI _V } for each time and frequency resource of the terminal allocated to the base station. Assuming that a 4-bit width PMI is used, {PMI _H (0), PMI _V (0)}, {PMI _H (1), PMI _V (0)}, ..., {PMI _H (15) , PMI _V (14)}, _{a precoding set corresponding to {PMI H} (15), PMI _V (15)} may be defined in advance according to the time and frequency resources specified in FIG. 14 . Hybrid MIMO communication can be used by using the precoding set {PMI _H , PMI _V } defined as above and methods 1 and 2 for defining the precoding set according to resources for each terminal. _{In an embodiment, a combination of {PMI H} , PMI _V } in each resource region shown in Table 1 may be applied differently depending on the embodiment.

Similar to the previous embodiment _{, the combination of {PMI H} , PMI _V } in the resource domain is one of the subband index, subframe index, C-RNTI mod N and cell id possessed by the terminal according to the user, time, and frequency resource. It can be assigned based on more than one value. In the case of subband-specific precoding definition method 5, each UE uses a predefined precoding set to define a precoding set according to a resource, using one or more of methods 1 and 2, 2D-CSI-RS currently possessing a precoding set. Alternatively, an optimal precoding set is derived by combining the reference signals H-CSI-RS and V-CSI-RS, and the rank and optimal precoding of the channel corresponding to one of these are delivered to the base station through one or more of RI and PMI. do.

The base station checks the precoding set based on the information received from the terminal, checks the precoding set corresponding to the received PMI, and considers 2D-CSI-RS or H-CSI-RS and V-CSI-RS simultaneously It is checked whether the CQI _HV is the maximum data rate considering any precoding.

In addition, as in the above example, in order to support multiple users by defining a precoding set in advance in a hybrid MIMO situation, it may be considered to allocate the precoding set defined in Table 1 to each user.

According to an embodiment, in the case of allocation for each wideband as in the precoding allocation method 2 according to time and frequency resources, the precoding allocation method may be defined for each wideband through one or more of the following methods.

- Precoding definition method for each wideband 1: Define PMI _H in advance.

- Precoding definition method for each wideband 2: Define PMI _V in advance.

- Precoding definition method for each wideband 3: Define PMI _H and PMI _V in advance for each terminal.

- Precoding definition method for each wideband 4: Define PMI _V and PMI _H in advance for each terminal.

- Precoding definition method for each wideband 5: Precoding set {PMI _H , PMI _V } is defined in advance.

15 is a diagram illustrating a method of pre-defining _{PMI H} for each time and frequency resource according to the wideband-specific precoding definition method 1 in each terminal according to an embodiment.

Referring to FIG. 15 , in an embodiment, PMI _H may be defined in advance through precoding definition method 1 for each wideband.

In the embodiment, assuming that a 4-bit width PMI is used _{, precoding corresponding to PMI H} (0), ..., PMI _H (15) may be defined in advance according to time and frequency resources as shown in FIG. 15 . there is. Hybrid MIMO communication can be used by using method 1 in _{which PMI H} and one precoding defined as above are defined according to resources. Allocation according to user, time, and frequency resource may be allocated based on at least one of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal.

At this time, when precoding is allocated to other terminals using adjacent time and frequency resources, such as identification number 1500 and identification number 1510, precoding allocation method to minimize the amount of signal interference that each terminal gives to the other terminal can be designed. In addition, although it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in the existing LTE, in order to support multiple users in a hybrid MIMO situation as in the example above, Likewise, it is necessary to allocate precoding for multiple users. The above example exemplifies that two terminals _{communicate with open-loop MIMO using the PMI H} promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

16 is a diagram illustrating a method of pre-defining _{PMI V} for each time and frequency resource according to method 2 for defining precoding for each wideband in each terminal according to an embodiment.

Referring to FIG. 16 , in the embodiment, PMI _V may be defined in advance through precoding definition method 2 for each wideband.

In the embodiment, assuming that a 4-bit width PMI is used _{, precoding corresponding to PMI V} (0), ..., PMI _V (15) can be defined in advance according to time and frequency resources as shown in FIG. 16 . there is. Hybrid MIMO communication can be used by using method 2 in _{which PMI V} defined as above and one precoding are defined according to resources. Allocation according to user, time, and frequency resource may be allocated based on at least one of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal.

At this time, when precoding is allocated to other terminals using adjacent time and frequency resources, such as identification number 1600 and identification number 1610, it can be designed to minimize the amount of signal interference that each terminal gives to the other terminal. there is.

In addition, in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE, it is assumed that one terminal communicates. Likewise, it is necessary to allocate precoding for multiple users. The above example exemplifies that two terminals _{communicate with open-loop MIMO using the PMI V} promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

17 is a diagram illustrating a method of pre-defining _{PMI H} and PMI _V for each terminal according to the wideband-specific precoding definition method 3 for each terminal according to an embodiment.

_{Referring to FIG. 17, PMI H} through precoding definition method 3 for each wideband and PMI _V may be defined in advance.

If it is assumed that PMI of 4 bit width is used in the embodiment, precoding corresponding to _{PMI H} (0), ..., PMI _H (15), PMI _V (0), ..., PMI _{V (15)} may be defined in advance according to time and frequency resources as shown in FIG. 17 . Hybrid MIMO communication can be used by using methods 1 and 2 for _{defining PMI H} and PMI _V defined as above and one precoding according to resources for each terminal. Like definition methods 1 and 2, allocation according to user, time, and frequency resource may be allocated using at least one of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal. In case of wideband-specific precoding definition method 3, UE0 uses PMI _H as an open-loop MIMO system, and UE1 uses PMI _V as an open-loop MIMO system to minimize interference between precodings assigned to each other.

Also, similar to the previous embodiment, it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE, but as in the above example, multiple users are used in a hybrid MIMO situation. In order to support it, it is necessary to allocate precoding to multiple users as shown in FIG. 17 . _{The above example exemplifies that two terminals communicate with open-loop MIMO using PMI H} and PMI _V and , which are promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a hybrid system, a more meticulous precoding definition design is required in consideration of the interference that each terminal gives to each other, unlike before. do.

18 is a diagram illustrating a method of pre-defining _{PMI V} and PMI _H for each terminal according to the wideband-specific precoding definition method 4 for each terminal according to an embodiment.

_{Referring to FIG. 18, PMI V} through precoding definition method 4 for each wideband and PMI _H may be defined in advance.

If it is assumed that PMI of 4 bit width is used in the embodiment, precoding corresponding to _{PMI H} (0), ..., PMI _H (15), PMI _V (0), ..., PMI _{V (15)} may be defined in advance according to time and frequency resources as shown in FIG. 18 . Hybrid MIMO communication can be used by using methods 1 and 2 for _{defining PMI H} and PMI _V defined as above and one precoding according to resources for each terminal. As in definition methods 1 and 2, allocation according to user, time, and frequency resource may be allocated based on one or more values of subband index, subframe index, C-RNTI mod N, and cell id possessed by the terminal.

In the embodiment, in the case of subband-specific precoding definition method 4, UE0 uses PMI _V as an open-loop MIMO system, and UE1 uses PMI _H as an open-loop MIMO system to minimize interference between precodings assigned to each other. can Also, similar to the previous embodiment, it is assumed that one terminal communicates in an open-loop MIMO system such as transmit diversity and large-delay CDD used in existing LTE. In order to support it, precoding may be assigned to multiple users as shown in FIG. 18 . _{The above example exemplifies that two terminals communicate with open-loop MIMO by using PMI H} and PMI _V and , which are promised by the base station, but it is similarly applicable to two or more terminals. In this case, unlike when two terminals communicate together using multi-user MIMO, when a plurality of terminals operate together in a Hybrid MIMO system, a more meticulous precoding definition design is required considering the interference that each terminal gives to each other, unlike the existing one. need.

19 illustrates an example of defining time and frequency resources for defining _{a plurality of precoding sets {PMI H} , PMI _V } in advance using the precoding definition method 5 for each wideband according to an embodiment.

Referring to FIG. 19, when time and frequency resources are allocated to apply precoding definition method 3 for each wideband, a precoding set {PMI _H , PMI _V } can be defined for each time and frequency resource as shown in Table 2 below. .

Table 2 below shows an example of a definition of a precoding set {PMI _H , PMI _{V } for each wideband.}

Table 2 above pre-defines the number of cases for _{a set of possible precodings {PMI H} , PMI _V } for each time and frequency resource of the terminal allocated to the base station. Table 2 will showing an example of a set of precoding PMI _{{H, V}} PMI combination in accordance with an embodiment, a set of precoding PMI _{{H, V}} PMI may be variously determined according to embodiments.

In the embodiment, assuming that a 4-bit width PMI is used, {PMI _H (0), PMI _V (0)}, {PMI _H (1), PMI _V (0)}, ..., {PMI _H A precoding set corresponding to (15), PMI _V (14)}, {PMI _H (15), PMI _V (15)} may be defined in advance according to the time and frequency resources specified in FIG. 19 . Hybrid MIMO communication can be used by using the precoding set {PMI _H , PMI _V } defined as above and methods 1 and 2 for defining the precoding set according to resources for each terminal. Similar to the previous embodiment, allocation according to user, time, and frequency resource may be allocated based on one or more values of a subband index, a subframe index, a C-RNTI mod N, and a cell id possessed by the terminal. In the case of subband-specific precoding definition method 5, each UE uses a predefined precoding set to define the previously described precoding set according to resources, using methods 1 and 2, the reference signal 2D-CSI-RS or An optimal precoding set is derived by combining with H-CSI-RS and V-CSI-RS, and the rank and optimal precoding of a channel corresponding to one of these can be delivered to the base station through at least one of RI and PMI.

The base station receives this and checks the precoding set corresponding to the received PMI to determine which precoding is considered by the CQI _{HV in} which 2D-CSI-RS or H-CSI-RS and V-CSI-RS are simultaneously considered. You can check the maximum data transfer rate. In addition, as in the above example, in order to support multiple users by pre-defining a precoding set in a Hybrid MIMO situation, it may be considered to allocate the precoding set defined in Table 2 to each user.

As mentioned above, the base station and the plurality of terminals can operate in an open-loop MIMO system using precodings defined in advance. In this case, it is necessary to define precoding for the base station and the plurality of terminals in advance. In the embodiment of the present specification, two methods are proposed as a method of defining precoding according to time and frequency resources between a base station and a plurality of terminals.

- Sharing precoding definition according to time and frequency resources Method 1: Use a predefined method (standard definition).

- Precoding definition sharing method according to time and frequency resources 2: The base station notifies through RRC or L1 signaling.

When using the Hybrid MIMO system according to the sharing method 1 of the precoding definition according to time and frequency resources, subband and Precoding is defined for each wideband. _{Accordingly, the corresponding base station and the terminal can communicate PMI H} and PMI _V in the Hybrid MIMO system as shown in FIGS. 6 to 9 using predefined precoding.

When using the Hybrid MIMO system according to the precoding definition sharing method 2 according to time and frequency resources, as shown in FIGS. 10 to 19 according to the precoding definition methods 1 and 2 according to time and frequency resources, to define precoding for each subband and wideband Additional RRC or L1 signaling is required for Through this, the corresponding base station and the terminal can communicate with the PMI _{H and the PMI V} using the Hybrid MIMO system as shown in 6 to 9 by using the predefined precoding.

As shown in FIGS. 6 and 7, when using a hybrid MIMO system by defining one precoding according to time and frequency resources using a method of defining one precoding according to resources, a predefined open-loop MIMO system The method for the closed-loop MIMO system to select the optimal precoding according to the precoding operating as follows is as follows.

- Precoding selection method of closed-loop MIMO system according to precoding of open-loop MIMO system 1: The optimal precoding is derived by considering all available precoder matrices defined in advance (through standards, etc.).

- Precoding selection method of closed-loop MIMO system according to precoding of open-loop MIMO system 2: The types of precoding available for closed-loop MIMO system are limited according to precoding of open-loop MIMO system.

Table 3 shows the case of selecting the optimal precoding for the closed-loop MIMO system by considering all the available precoder matrices defined in the standard according to method 1 of the precoding selection method for the closed-loop MIMO system according to the precoding of the open-loop MIMO system. .

It shows how to consider all available precoder matrices defined in the standard below.

As shown in Table 3 above, each of PMI _H and PMI _V can be considered for all relative PMI _V and PMI _H , and accordingly, CQI _HV It is possible to derive the radio channel state by considering all the relative precoder matrices during derivation.

In general, depending on what the precoding in the vertical direction is, the precoding in the horizontal direction that is optimal for the terminal may vary. In consideration of such radio channel characteristics, the present invention proposes a two-dimensional PMI restriction technique. In general, PMI restriction limits the range of PMI that the terminal can select and notify. In this way, when the PMI restriction is applied, the terminal searches within a smaller range in the process of selecting the optimal PMI, thereby reducing the complexity of the terminal's operation or reducing the PMI overhead that the terminal notifies to the base station. It works.

According to the method 2 of selecting the precoding of the closed-loop MIMO system according to the precoding of the open-loop MIMO system proposed in the embodiment of the present specification, the type of precoding that can be used according to the precoding of the open-loop MIMO system is limited to the standard. The method includes limiting the PMI that can be designated in the closed loop according to the precoding determined according to the open-loop MIMO.

That is, when the UE _{assumes PMI V} (0), PMI _H is selected only within PMI values specified for PMI _V(0). In addition, if PMI _V (1) is assumed, PMI _H is selected only within the PMI values specified for PMI _V(1). That is, the range of _{the PMI H} value that the UE can select is limited according to what the _{PMI V} value to be assumed by the UE is. When the PMI restriction according to the embodiment of the present specification is applied, the range of _{PMI H} selected by the closed-loop MIMO scheme varies according _{to the PMI V value determined by the open-loop MIMO.}

The method of limiting the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system in the standard according to the selection method 2 of the precoding of the closed-loop MIMO system according to the precoding of the open-loop MIMO system includes one or more of the following do.

- Method to limit the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system 1: Restriction depending on the case of _{PMI H} and PMI _V

- Method 2: Limiting the types of precoding of the usable closed-loop MIMO system according to the precoding of the open-loop MIMO system: Restricting only a _{specific PMI H}

- Method 3 for limiting the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system: Restricting only a _{specific PMI V}

Table 4 below is a table showing restrictions on _{PMI H} and PMI _V according to the precoding selection method 1 of the closed-loop MIMO system according to the precoding of the open-loop MIMO system.

More specifically, Table 4 below shows the restrictions depending on the case of _{PMI H} and PMI _V.

As shown in Table 4 above, each PMI _H and PMI _V is the CQI _HV for each relative PMI _V and PMI _H. It is decided whether or not to be considered in the derivation. A combination of whether to consider each corresponding PMI in Table 4 may be variously determined according to embodiments.

In the embodiment, in the case of the setting method shown in Table 4, since all PMI _H and PMI _V are set, it is advantageous for optimizing each performance. On the other hand, sharing these predefined definitions through standards or receiving them through signals requires a lot of resources.

_{Table 5 below shows the precoding set {PMI H} , PMI _V } in order to operate with methods 1 and 2 for defining the precoding set according to resources using the precoding selection method 1 of the closed-loop MIMO system according to the precoding of the open-loop MIMO system. This table shows the definition.

More specifically, Table 5 below shows that the precoding set {PMI _H , PMI _V } is defined.

As shown in Table 5 above, since each of PMI _H and PMI _V can be considered only for one relative PMI _V and PMI _{H , even if only one value of PMI H} and PMI _V is received, the relative value is checked and the CQI is considered as a whole. _HV It is possible to determine what kind of precoding is considered the maximum possible data rate set. A combination of whether to consider each corresponding PMI in Table 5 may be variously determined according to embodiments.

In the embodiment, in the case of such a setting method, it _{is not assumed that feedback is given for a specific PMI H} or PMI _V , and the number of cases can be identified and confirmed even if only one value is raised, so that it can be flexibly dealt with depending on the situation, and H-CSI-RS and V-CSI-RS can be actively dealt with, and there is an effect of reducing overhead according to PMI reporting.

Table 6 below is a table showing that only a _{specific PMI H} is limited according to method 2 of restricting the types of precoding of a closed-loop MIMO system that can be used according to the precoding of an open-loop MIMO system.

More specifically, Table 6 below shows a method of limiting only a _{specific PMI H.}

As shown in Table 6 above, in method 2 of limiting the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system, the base station sets not to use only a _{specific PMI H , so that each PMI V} is a specific PMI. CQI _{HV for H only} It is not taken into account in derivation. _{PMI H} not to be used according to an embodiment may be determined in various ways.

Therefore, according to an embodiment, since such a predefined definition is shared between the terminal and the base station through a standard or _{only a specific PMI H} to be excluded when received through signal transmission between the terminal and the base station is shared or transmitted, the precoding of the open-loop MIMO system Unlike method 1, which restricts the types of precoding of the closed-loop MIMO system that can be used according to However, it is impossible to set _{PMI H} and PMI _V more precisely than Method 1 which limits the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system. there is. Also, in the above example, _{only one PMI H} is limited, but if necessary, it is possible to limit a _{plurality of PMI Hs.}

Table 7 below is a table showing that only a _{specific PMI V} is limited according to method 3 for limiting the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system.

More specifically, Table 7 below shows a method of limiting only a _{specific PMI V.}

As shown in Table 7 above, in method 3 of limiting the types of precoding of the closed-loop MIMO system that can be used according to the precoding of the open-loop MIMO system, the base station sets not to use only a _{specific PMI V , so that each PMI H} is a specific PMI. CQI _{HV for V only} It may not be taken into account in the derivation. _{PMI V} not to be used may be determined differently according to an embodiment.

Therefore, it is only necessary to share or transmit PMI information that is not to be used between the base station and the terminal through the standard definition, or to share or transmit only a _{specific PMI V to be excluded when receiving the PMI information between the base station and the terminal through signal transmission.} Unlike method 1, which restricts the types of precoding of a usable closed-loop MIMO system according to system precoding, it is possible to limit using a relatively small number of downlink control resources. However, it may be difficult to set _{PMI H} and PMI _V more precisely than Method 1 for limiting the types of precoding available in the closed-loop MIMO system according to the precoding of the open-loop MIMO system. Further, in the above example, but are limited to only one PMI _V, it is possible to limit to a plurality of PMI _V if necessary.

At least one of methods 1, 2, and 3 of precoding limiting methods 1, 2, and 3 of a closed-loop MIMO system according to the precoding of an open-loop MIMO system may be simultaneously applied according to circumstances. It can be assumed that precoding restrictions as shown in Table 4 are defined through standards by method 1 of the precoding restriction of the closed-loop MIMO system according to the precoding of the open-loop MIMO system. At this time, it would have been assumed that the precoding restriction signal as shown in Table 7 was transmitted using the precoding restriction method 3 of the closed-loop MIMO system according to the precoding of the open-loop MIMO system through one or more of the RRC, L1 siganling, and downlink control signals. In this case, the precoding restrictions of the closed-loop MIMO system according to the precoding of the open-loop MIMO system recognized by the base station and the terminal are shown in Table 8 below.

More specifically, Table 8 below shows an example of a method of restricting precoding by combining methods 1 and 3 for limiting precoding of a closed-loop MIMO system according to precoding of an open-loop MIMO system.

Table way to limit the precoding types of closed-loop MIMO system usable in accordance with the precoding of the open-loop MIMO system, as described in 8 are considered in the first and third received additionally each PMI _H and PMI _V, as well as Table 5 Similarly for a specific PMI _V , the optimal precoding calculation and CQI _HV It can be confirmed that the derivation is not taken into account. A combination of precoding not to be considered according to an embodiment may be determined in various ways.

In this way, according to the precoding of the open-loop MIMO system, the types of precoding of the closed-loop MIMO system that can be used are limited. For PMI _H and PMI _{V detailed in method 1, additional CQI HV} is added according to the channel state between the base station and the terminal. You can set _{PMI H} or PMI _V to be excluded from calculation.

20 is a diagram illustrating an operation of a base station in method 1 of defining one precoding according to a resource according to an embodiment of the present specification.

Referring to FIG. 20 , in step 2000, the base station transmits to the terminal at least one of a reference signal and configuration information related to channel information reporting to the terminal.

In step 2010, the base station may check which precoding corresponds to _{the RI H} and PMI _H predefined according to the time and frequency resource for the terminal to receive the CSI-RS. According to an embodiment, the step 2010 may be known based on preset information by the base station without a separate operation.

In step 2020, the base station determines a channel obtained by applying a predefined horizontal precoding to the 2D-CSI-RS received from the terminal or a channel obtained by measuring a vertical CSI-RS (V-CSI-RS). The rank of _{the corresponding channel can be determined by receiving RI V,} which is the rank, and PMI _V and CQI _HV can also be received and confirmed.

In step 2030, the base station determines the maximum data rate CQI _{HV derived by simultaneously assuming predefined RI H} , PMI _H and received RI _V , PMI _V , and transmits a control signal to the terminal according to the determination. In an embodiment, the base station may determine the _{CQI HV} based on one or more of the information transmitted in step 2000 . Also, thereafter, the base station may transmit/receive a data signal to/from the terminal according to the determination.

21 is a diagram illustrating the operation of a terminal in method 1 of defining one precoding according to a resource according to an embodiment of the present specification.

Referring to FIG. 21 , in step 2100, the terminal may receive at least one of a reference signal and configuration information related to channel information reporting from the base station.

In step 2110, the UE checks which precoding corresponds to _{the RI H} and PMI _H predefined according to the time and frequency resource for receiving the CSI-RS. According to an embodiment, the step 2110 may be known by the terminal based on preset information without a separate operation.

In step 2120, the UE measures the channel or vertical CSI-RS (V-CSI-RS) obtained by applying a predefined horizontal precoding to the 2D-CSI-RS to obtain the rank of the channel, and sends the RI _{V to the base station.} may be notified through

In step 2130, in order to determine the optimal precoding after the _{RI V} notification, the UE may determine the optimal precoding by simultaneously assuming _{predefined RI H} , PMI _H and derived RI _{V .}

In step 2140, the terminal calculates the maximum data rate corresponding to the determined optimal precoding and transmits it to the base station through _{PMI V} and CQI _HV.

Thereafter, the terminal may receive data from the base station based on the information transmitted to the base station.

22 is a diagram illustrating an operation of a base station in method 2 of defining one precoding according to a resource according to an embodiment of the present specification.

Referring to FIG. 22, in step 2200, the base station notifies the terminal of at least one of configuration information related to a reference signal and channel information reporting to the terminal.

In step 2210, the base station can check which precoding corresponds to _{the RI V} and PMI _V predefined according to the time and frequency resources for the terminal to receive the CSI-RS. According to an embodiment, the step 2210 may be known by the base station based on preset information without a separate operation.

In step 2220, the base station obtains a channel obtained by applying a predefined vertical precoding to the 2D-CSI-RS received from the terminal or a channel obtained by measuring a horizontal CSI-RS (H-CSI-RS). It can be confirmed _{by receiving RI H,} which is the rank, to determine the rank of the corresponding channel, and by receiving PMI _H and CQI _HV.

In step 2230, the base station determines the maximum data rate CQI _{HV derived by simultaneously assuming predefined RI V} , PMI _V and received RI _H , PMI _H , and sends a control signal to the terminal according to the determination In , the base station may determine _{the CQI HV} by additionally considering one or more of the information transmitted in step 2200. Also, thereafter, the base station may transmit/receive a data signal to/from the terminal according to the determination.

23 is a diagram illustrating the operation of a terminal in method 2 of defining one precoding according to a resource according to an embodiment of the present specification.

Referring to FIG. 23 , in step 2300, the terminal may receive at least one of a reference signal and configuration information related to channel information reporting from the base station.

In step 2310, the UE checks which precoding corresponds to _{the RI V} and PMI _V predefined according to the time and frequency resource for receiving the CSI-RS. According to an embodiment, the step 2310 may be known by the terminal based on preset information without a separate operation.

In step 2320, the UE measures the channel obtained by applying a predefined vertical precoding to the 2D-CSI-RS or CSI-RS (H-CSI-RS) in the horizontal direction to obtain the rank of the channel and RI to the base station _H can be notified.

In step 2330, _{after the RI H} notification, the terminal may determine _{the optimal precoding by simultaneously assuming predefined RI V} , PMI _V and derived RI _V in order to determine the optimal precoding.

In step 2340, the terminal calculates the maximum data rate corresponding to the determined optimal precoding and transmits it to the base station through _{PMI H} and CQI _HV.

Thereafter, the terminal may receive data from the base station based on the information transmitted to the base station.

24 is a diagram illustrating an operation of a base station in method 1 of defining a precoding set according to a resource according to an embodiment of the present specification.

Referring to FIG. 24 , in step 2400, the base station notifies the terminal of at least one of a reference signal and configuration information related to channel information reporting to the terminal.

_{In step 2410, the base station can check which of the predefined RI H} and the corresponding precoding set {PMI _H , PMI _V } according to the time and frequency resource for the terminal to receive the CSI-RS. According to an embodiment, in step 2410, the base station may check based on preset information without a separate operation.

In step 2420, the base station determines a channel obtained by applying a predefined horizontal precoding to the 2D-CSI-RS received from the terminal or a channel obtained by measuring a vertical CSI-RS (V-CSI-RS). The rank of the corresponding channel can be determined by receiving the _{RI V,} which is the rank, and _{can be confirmed by receiving the PMI V} and CQI _HV.

In step 2430, the base station checks the _{predefined RI H} and the predefined precoding set {PMI _H , PMI _{V } corresponding to the received RI V} through the received PMI _V.

In step 2440, the base station _{determines the maximum data rate CQI HV} derived by simultaneously assuming one or more _{of RI H} , PMI _H , RI _V and PMI _V , and transmits a control signal to the terminal according to the determination. In an embodiment, the base station may determine _{the CQI HV} by additionally considering one or more of the information transmitted in step 2400 . Also, thereafter, the base station may transmit/receive a data signal to/from the terminal according to the determination.

25 is a diagram illustrating the operation of a terminal in method 1 of defining a precoding set according to a resource according to an embodiment of the present specification.

Referring to FIG. 25 , in step 2500 , the terminal may receive at least one of a reference signal and configuration information related to channel information reporting from the base station.

_{In step 2510, the UE determines which RI H} and the corresponding precoding set {PMI _H , PMI _V } are predefined according to time and frequency resources for receiving the CSI-RS. According to an embodiment, the step 2510 may be known by the terminal based on preset information without a separate operation.

In step 2520, the UE measures a channel obtained by applying predefined horizontal precoding to 2D-CSI-RS or CSI-RS (V-CSI-RS) in the vertical direction to obtain the rank of the channel, and provides the RI to the base station. _V can be notified.

_{After the RI V} notification in step 2530, the terminal assumes the predefined precoding set {PMI _H , PMI _V } _{corresponding to the predefined RI H} and the derived RI _V to determine the optimal precoding. You can decide on precoding.

In step 2540, the terminal may _{transmit a value corresponding to PMI V} among the thus determined optimal precoding set to the base station delivery.

In step 2550, the terminal may obtain the maximum data rate corresponding to _{the PMI V} and transmit it to the base station through the _{CQI HV.}

Thereafter, the terminal may receive data from the base station based on the information transmitted to the base station.

26 is a diagram illustrating the operation of a base station in method 2 of defining a precoding set according to a resource according to an embodiment of the present specification.

Referring to FIG. 26, in step 2600, the base station notifies the terminal of at least one of configuration information related to a reference signal and channel information reporting to the terminal.

_{In step 2610, the base station can check which of the predefined RI V} and the corresponding precoding set {PMI _H , PMI _V } according to the time and frequency resource for the terminal to receive the CSI-RS. According to an embodiment, in step 2610, the base station may check based on preset information without a separate operation.

In step 2620, the base station determines a channel obtained by applying a predefined vertical precoding to the 2D-CSI-RS received from the terminal or a channel obtained by measuring a horizontal CSI-RS (H-CSI-RS). The rank of the corresponding channel can be determined by receiving _{RI H,} which is the rank, and _{can be confirmed by receiving PMI H} and CQI _HV.

In step 2630, the base station checks the _{predefined RI V} and the predefined precoding set {PMI _H , PMI _{V } corresponding to the received RI H} through the received PMI _V.

In step 2640, the base station determines the maximum data rate CQI _{HV derived by assuming at least one of RI H} , PMI _H , RI _V and PMI _V at the same time, and transmits a control signal to the terminal according to the determination. In an embodiment, the base station may determine _{the CQI HV} by additionally considering one or more of the information transmitted in step 2600 . Also, thereafter, the base station may transmit/receive a data signal to/from the terminal according to the determination.

27 is a diagram illustrating the operation of a terminal in method 2 of defining a precoding set according to a resource according to an embodiment of the present specification.

Referring to FIG. 27 , in step 2700, the terminal receives at least one of a reference signal and configuration information related to channel information reporting from the base station.

Precoding set in step 2710 to the user terminal that the RI _V defined in advance and depending on the time and frequency resources to receive channel or the CSI-RS is obtained by applying the precoding in the vertical direction are defined in advance in the 2D-CSI-RS { You can check what _{PMI H} , PMI _{V } is.} According to an embodiment, the step 2710 may be known by the terminal based on preset information without a separate operation.

In step 2720, the UE measures the channel obtained by applying a predefined vertical precoding to the 2D-CSI-RS or CSI-RS (H-CSI-RS) in the horizontal direction to obtain the rank of the channel and RI to the base station _H can be notified.

_{After the RI H} notification in step 2730, the terminal assumes the predefined precoding set {PMI _H , PMI _V } _{corresponding to the predefined RI V} and the derived RI _H in order to determine the optimal precoding. You can decide on precoding.

In step 2740, the terminal may transmit a value corresponding to _{PMI H among the determined optimal precoding set to the base station.}

In step 2750, the terminal may obtain the maximum data rate corresponding to _{the PMI H} and transmit it to the base station through the _{CQI HV.}

28 is a diagram illustrating an apparatus of a base station in an FD-MIMO system according to an embodiment of the present specification.

Referring to FIG. 28 , the base station according to the embodiment may include at least one of a base station controller 2800 , a transmitter 2810 , and a receiver 2820 . The base station controller 2800 may control the overall operation of the base station, and may determine a value related to the base station operation based on transmitted/received information.

The base station according to the embodiment may determine how to configure the 2D-CSI-RS or a plurality of CSI-RSs using the base station controller 2800 .

According to an embodiment, the base station controller 2800 may control the transmitter 2810 to notify the terminal of a signal based on the determination result.

In addition, the base station controller 2800 may determine how to set the channel state information to be transmitted by the terminal, and control the transmitter 2810 to notify the terminal of the determination result. Also, the base station controller 2800 may control the transmitter 2810 to transmit a 2D-CSI-RS or a plurality of CSI-RSs to the terminal.

Also, in an embodiment, the base station controller 2800 may set the CSI-RS and channel state information of the terminal, and control the receiver 2820 to receive the channel state information notified by the terminal.

29 is a diagram illustrating a device of a terminal in an FD-MIMO system according to an embodiment of the present specification.

Referring to FIG. 29 , a terminal (terminal) according to an embodiment may include at least one of a terminal controller 2900 , a transmitter 2910 , and a receiver 2920 . The terminal controller 2900 may control the overall operation of the terminal, and may determine a value related to the operation of the terminal based on transmitted and received information.

In an embodiment, the terminal controller 2900 controls the receiver 2920 to configure and report configuration information and channel state information for the 2D-CSI-RS or a plurality of CSI-RSs from the base station to the base station. One or more of these may be notified.

Based on the information received from the base station, the terminal controller 2900 may control reception of the terminal's 2D-CSI-RS or a plurality of CSI-RSs.

Also, the terminal controller 2900 may control the receiver 2920 to receive a plurality of CSI-RSs.

Also, the terminal controller 2900 may generate channel state information generated based on the received plurality of CSI-RSs, and control the transmitter 2910 to report the generated channel state information to the base station.

On the other hand, in the present specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms are used, these are only used in a general sense to easily explain the technical content of the present invention and help the understanding of the present invention, It is not intended to limit the scope of the invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

100: base station transmission equipment
110: transmit antenna
120, 130: transmit/receive signal

Claims (28)

A method for transmitting and receiving channel state information performed by a terminal of a communication system, the method comprising:
Receiving information indicating a set of pre-determined precoders that can be assumed associated with a second precoding matrix indicator (PMI) from the base station through radio resource control (RRC) signaling;
obtaining a first PMI related to a channel state information reference signal (CSI-RS);
obtaining a channel quality indicator (CQI) based on at least one precoder defined based on the first PMI and at least one hypothesized second PMI; and
and transmitting the first PMI and the CQI to the base station. The method of claim 1, wherein only the first PMI is transmitted among the first PMI and the second PMI. The method of claim 1, wherein the at least one precoder corresponds to each subband. The method of claim 1, wherein a rank indicator (RI) is shared between the terminal and the base station. delete A method for transmitting and receiving channel state information performed by a base station of a communication system, the method comprising:
Transmitting information indicating a set of a predetermined precoder (precoder) that can be assumed related to a second precoding matrix indicator (PMI) to the terminal through radio resource control (RRC) signaling; and
Receiving a first PMI and a channel quality indicator (CQI) related to a channel state information reference signal (CSI-RS) from the terminal,
The CQI is associated with at least one precoder defined based on the first PMI and at least one hypothesized second PMI. The method of claim 6, wherein only the first PMI among the first PMI and the second PMI is received. The method of claim 6, wherein the at least one precoder corresponds to each subband. The method of claim 6, wherein a rank indicator (RI) is shared between the terminal and the base station. delete In the terminal of a communication system,
a transceiver including a plurality of antennas and transmitting and receiving signals to and from the base station; and
Control the transceiver and receive information indicating a set of pre-determined precoders that can be assumed related to a second precoding matrix indicator (PMI) from the base station through radio resource control (RRC) signaling, and a channel Acquire a first PMI related to a channel state information reference signal (CSI-RS), and based on at least one precoder defined based on the first PMI and at least one hypothesized second PMI Obtaining a channel quality indicator (CQI) and comprising a control unit for controlling to transmit the first PMI and the CQI to the base station. The terminal of claim 11, wherein only the first PMI among the first PMI and the second PMI is transmitted. The terminal of claim 11, wherein the at least one precoder corresponds to each subband. The terminal of claim 11, wherein a rank indicator (RI) is shared between the terminal and the base station. delete In a base station of a communication system,
a transceiver including a plurality of antennas and transmitting and receiving signals to and from the terminal;
Controls the transceiver, and transmits information indicating a set of predetermined precoders that can be assumed related to a second precoding matrix indicator (PMI) to the terminal through radio resource control (RRC) signaling, and the A control unit for controlling to receive a first PMI and a channel quality indicator (CQI) related to a channel state information reference signal (CSI-RS) from the terminal,
The CQI is associated with at least one precoder defined based on the first PMI and at least one hypothesized second PMI. The base station of claim 16, wherein only the first PMI among the first PMI and the second PMI is received. The base station of claim 16, wherein the at least one precoder corresponds to each subband. The base station of claim 16, wherein a rank indicator (RI) is shared between the terminal and the base station. delete delete delete delete delete delete delete delete delete

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